Project: OpenAPI (App Definition and Development / Application Definition & Image Build)
File: 3.0.2.md

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in when, and only when, they appear in all capitals, as shown here. This document is licensed under . The OpenAPI Specification (OAS) defines a standard, language-agnostic interface to RESTful APIs which allows both humans and computers to discover and understand the capabilities of the service without access to source code, documentation, or through network traffic inspection. When properly defined, a consumer can understand and interact with the remote service with a minimal amount of implementation logic. An OpenAPI definition can then be used by documentation generation tools to display the API, code generation tools to generate servers and clients in various programming languages, testing tools, and many other use cases. <!-- TOC depthFrom:1 depthTo:3 withLinks:1 updateOnSave:1 orderedList:0 --> - - - - - - - - - - - - - - - - - - - - - - <!-- /TOC --> A document (or set of documents) that defines or describes an API. An OpenAPI definition uses and conforms to the OpenAPI Specification. Path templating refers to the usage of curly braces ({}) to mark a section of a URL path as replaceable using path parameters. Media type definitions are spread across several resources. The media type definitions SHOULD be in compliance with . Some examples of possible media type definitions: ``` text/plain; charset=utf-8 application/json application/vnd.github+json application/vnd.github.v3+json application/vnd.github.v3.raw+json application/vnd.github.v3.text+json application/vnd.github.v3.html+json application/vnd.github.v3.full+json application/vnd.github.v3.diff application/vnd.github.v3.patch ``` The HTTP Status Codes are used to indicate the status of the executed operation. The available status codes are defined by and registered status codes are listed in the . The OpenAPI Specification is versioned using (semver) and follows the semver specification. The `major`.`minor` portion of the semver (for example `3.0`) SHALL designate the OAS feature set. Typically, `.patch` versions address errors in this document, not the feature set. Tooling which supports OAS 3.0 SHOULD be compatible with all OAS 3.0.\* versions. The patch version SHOULD NOT be considered by tooling, making no distinction between `3.0.0` and `3.0.1` for example. Subsequent minor version releases of the OpenAPI Specification (incrementing the `minor` version number) SHOULD NOT interfere with tooling developed to a lower minor version and same major version. Thus a hypothetical `3.1.0` specification SHOULD be usable with tooling designed for `3.0.0`. An OpenAPI document compatible with OAS 3.\.\ contains a required field which designates the semantic version of the OAS that it uses. (OAS 2.0 documents contain a top-level version field named and value `"2.0"`.) An OpenAPI document that conforms to the OpenAPI Specification is itself a JSON object, which may be represented either in JSON or YAML format. For example, if a field has an array value, the JSON array representation will be used: ```json { "field": [ 1, 2, 3 ] } ``` All field names in the specification are case sensitive. This includes all fields that are used as keys in a map, except where explicitly noted that keys are case insensitive. The schema exposes two types of fields: Fixed fields, which have a declared name, and Patterned fields, which declare a regex pattern for the field name. Patterned fields MUST have unique names within the containing object. In order to preserve the ability to round-trip between YAML and JSON formats, YAML version is RECOMMENDED along with some additional constraints: Tags MUST be limited to those allowed by the

Keys used in YAML maps MUST be limited to a scalar string, as defined by the . Note: While APIs may be defined by OpenAPI documents in either YAML or JSON format, the API request and response bodies and other content are not required to be JSON or YAML. An OpenAPI document MAY be made up of a single document or be divided into multiple, connected parts at the discretion of the user. In the latter case, `$ref` fields MUST be used in the specification to reference those parts as follows from the definitions. It is RECOMMENDED that the root OpenAPI document be named: `openapi.json` or `openapi.yaml`. Primitive data types in the OAS are based on the types supported by the . Note that `integer` as a type is also supported and is defined as a JSON number without a fraction or exponent part. `null` is not supported as a type (see for an alternative solution). Models are defined using the , which is an extended subset of JSON Schema Specification Wright Draft 00. <a name="dataTypeFormat"></a>Primitives have an optional modifier property: `format`. OAS uses several known formats to define in fine detail the data type being used. However, to support documentation needs, the `format` property is an open `string`-valued property, and can have any value. Formats such as `"email"`, `"uuid"`, and so on, MAY be used even though undefined by this specification. Types that are not accompanied by a `format` property follow the type definition in the JSON Schema. Tools that do not recognize a specific `format` MAY default back to the `type` alone, as if the `format` is not specified. The formats defined by the OAS are: | | Comments | -- | -- `integer` | `int32` | signed 32 bits `integer` | `int64` | signed 64 bits (a.k.a long) `number` | `float` | | `number` | `double` | | `string` | | | `string` | `byte` | base64 encoded characters `string` | `binary` | any sequence of octets `boolean` | | | `string` | `date` | As defined by `full-date` - `string` | `date-time` | As defined by `date-time` - `string` | `password` | A hint to UIs to obscure input. Throughout the specification `description` fields are noted as supporting CommonMark markdown formatting. Where OpenAPI tooling renders rich text it MUST support, at a minimum, markdown syntax as described by . Tooling MAY choose to ignore some CommonMark features to address security concerns. Unless specified otherwise, all properties that are URLs MAY be relative references as defined by . Relative references are resolved using the URLs defined in the as a Base URI. Relative references used in `$ref` are processed as per , using the URL of the current document as the base URI. See also the . In the following description, if a field is not explicitly REQUIRED or described with a MUST or SHALL, it can be considered OPTIONAL. This is the root document object of the . Field Name | Type | Description |::| <a name="oasVersion"></a>openapi | `string` | REQUIRED. This string MUST be the of the that the OpenAPI document uses. The `openapi` field SHOULD be used by tooling specifications and clients to interpret the OpenAPI document. This is not related to the API string. <a name="oasInfo"></a>info | | REQUIRED. Provides metadata about the API. The metadata MAY be used by tooling as required. <a name="oasServers"></a>servers | ] | An array of Server Objects, which provide connectivity information to a target

If the `servers` property is not provided, or is an empty array, the default value would be a with a value of `/`. <a name="oasPaths"></a>paths | | REQUIRED. The available paths and operations for the API. <a name="oasComponents"></a>components | | An element to hold various schemas for the specification. <a name="oasSecurity"></a>security | ] | A declaration of which security mechanisms can be used across the API. The list of values includes alternative security requirement objects that can be used. Only one of the security requirement objects need to be satisfied to authorize a request. Individual operations can override this definition. <a name="oasTags"></a>tags | ] | A list of tags used by the specification with additional metadata. The order of the tags can be used to reflect on their order by the parsing tools. Not all tags that are used by the must be declared. The tags that are not declared MAY be organized randomly or based on the tools' logic. Each tag name in the list MUST be unique. <a name="oasExternalDocs"></a>externalDocs | | Additional external documentation. This object MAY be extended with . The object provides metadata about the API. The metadata MAY be used by the clients if needed, and MAY be presented in editing or documentation generation tools for convenience. Field Name | Type | Description |::| <a name="infoTitle"></a>title | `string` | REQUIRED. The title of the application. <a name="infoDescription"></a>description | `string` | A short description of the application. MAY be used for rich text representation. <a name="infoTermsOfService"></a>termsOfService | `string` | A URL to the Terms of Service for the API. MUST be in the format of a URL. <a name="infoContact"></a>contact | | The contact information for the exposed API. <a name="infoLicense"></a>license | | The license information for the exposed API. <a name="infoVersion"></a>version | `string` | REQUIRED. The version of the OpenAPI document (which is distinct from the or the API implementation version). This object MAY be extended with . ```json { "title": "Sample Pet Store App", "description": "This is a sample server for a pet store.", "termsOfService": "http://example.com/terms/", "contact": { "name": "API Support", "url": "http://www.example.com/support", "email": "support@example.com" }, "license": { "name": "Apache 2.0", "url": "https://www.apache.org/licenses/LICENSE-2.0.html" }, "version": "1.0.1" } ``` ```yaml title: Sample Pet Store App description: This is a sample server for a pet store. termsOfService: http://example.com/terms/ contact: name: API Support url: http://www.example.com/support email: support@example.com license: name: Apache 2.0 url: https://www.apache.org/licenses/LICENSE-2.0.html version: 1.0.1 ``` Contact information for the exposed API. Field Name | Type | Description |::| <a name="contactName"></a>name | `string` | The identifying name of the contact person/organization. <a name="contactUrl"></a>url | `string` | The URL pointing to the contact information. MUST be in the format of a URL. <a name="contactEmail"></a>email | `string` | The email address of the contact person/organization. MUST be in the format of an email address. This object MAY be extended with . ```json { "name": "API Support", "url": "http://www.example.com/support", "email": "support@example.com" } ``` ```yaml name: API Support url: http://www.example.com/support email: support@example.com ``` License information for the exposed API. Field Name | Type | Description |::| <a name="licenseName"></a>name | `string` | REQUIRED. The license name used for the API. <a name="licenseUrl"></a>url | `string` | A URL to the license used for the API. MUST be in the format of a URL. This object MAY be extended with . ```json { "name": "Apache 2.0", "url": "https://www.apache.org/licenses/LICENSE-2.0.html" } ``` ```yaml name: Apache 2.0 url: https://www.apache.org/licenses/LICENSE-2.0.html ``` An object representing a Server. Field Name | Type | Description |::| <a name="serverUrl"></a>url | `string` | REQUIRED. A URL to the target

This URL supports Server Variables and MAY be relative, to indicate that the host location is relative to the location where the OpenAPI document is being served. Variable substitutions will be made when a variable is named in `{`brackets`}`. <a name="serverDescription"></a>description | `string` | An optional string describing the host designated by the URL. MAY be used for rich text representation. <a name="serverVariables"></a>variables | Map] | A map between a variable name and its value. The value is used for substitution in the server's URL template. This object MAY be extended with . A single server would be described as: ```json { "url": "https://development.gigantic-server.com/v1", "description": "Development server" } ``` ```yaml url: https://development.gigantic-server.com/v1 description: Development server ``` The following shows how multiple servers can be described, for example, at the OpenAPI Object's : ```json { "servers": [ { "url": "https://development.gigantic-server.com/v1", "description": "Development server" }, { "url": "https://staging.gigantic-server.com/v1", "description": "Staging server" }, { "url": "https://api.gigantic-server.com/v1", "description": "Production server" } ] } ``` ```yaml servers: url: https://development.gigantic-server.com/v1 description: Development server url: https://staging.gigantic-server.com/v1 description: Staging server url: https://api.gigantic-server.com/v1 description: Production server ``` The following shows how variables can be used for a server configuration: ```json { "servers": [ { "url": "https://{username}.gigantic-server.com:{port}/{basePath}", "description": "The production API server", "variables": { "username": { "default": "demo", "description": "this value is assigned by the service provider, in this example `gigantic-server.com`" }, "port": { "enum": [ "8443", "443" ], "default": "8443" }, "basePath": { "default": "v2" } } } ] } ``` ```yaml servers: url: https://{username}.gigantic-server.com:{port}/{basePath} description: The production API server variables: username: default: demo description: this value is assigned by the service provider, in this example `gigantic-server.com` port: enum: '8443' '443' default: '8443' basePath: default: v2 ``` An object representing a Server Variable for server URL template substitution. Field Name | Type | Description |::| <a name="serverVariableEnum"></a>enum | [`string`] | An enumeration of string values to be used if the substitution options are from a limited set. <a name="serverVariableDefault"></a>default | `string` | REQUIRED. The default value to use for substitution, which SHALL be sent if an alternate value is not supplied. Note this behavior is different than the treatment of default values, because in those cases parameter values are optional. <a name="serverVariableDescription"></a>description | `string` | An optional description for the server variable. MAY be used for rich text representation. This object MAY be extended with . Holds a set of reusable objects for different aspects of the OAS. All objects defined within the components object will have no effect on the API unless they are explicitly referenced from properties outside the components object. Field Name | Type | Description |:| <a name="componentsSchemas"></a> schemas | Map \| ] | An object to hold reusable . <a name="componentsResponses"></a> responses | Map \| ] | An object to hold reusable . <a name="componentsParameters"></a> parameters | Map \| ] | An object to hold reusable . <a name="componentsExamples"></a> examples | Map \| ] | An object to hold reusable . <a name="componentsRequestBodies"></a> requestBodies | Map \| ] | An object to hold reusable . <a name="componentsHeaders"></a> headers | Map \| ] | An object to hold reusable . <a name="componentsSecuritySchemes"></a> securitySchemes| Map \| ] | An object to hold reusable . <a name="componentsLinks"></a> links | Map \| ] | An object to hold reusable . <a name="componentsCallbacks"></a> callbacks | Map \| ] | An object to hold reusable . This object MAY be extended with . All the fixed fields declared above are objects that MUST use keys that match the regular expression:

Field Name Examples: ``` User User_1 User_Name user-name my.org.User ``` ```json "components": { "schemas": { "GeneralError": { "type": "object", "properties": { "code": { "type": "integer", "format": "int32" }, "message": { "type": "string" } } }, "Category": { "type": "object", "properties": { "id": { "type": "integer", "format": "int64" }, "name": { "type": "string" } } }, "Tag": { "type": "object", "properties": { "id": { "type": "integer", "format": "int64" }, "name": { "type": "string" } } } }, "parameters": { "skipParam": { "name": "skip", "in": "query", "description": "number of items to skip", "required": true, "schema": { "type": "integer", "format": "int32" } }, "limitParam": { "name": "limit", "in": "query", "description": "max records to return", "required": true, "schema" : { "type": "integer", "format": "int32" } } }, "responses": { "NotFound": { "description": "Entity not found." }, "IllegalInput": { "description": "Illegal input for operation." }, "GeneralError": { "description": "General Error", "content": { "application/json": { "schema": { "$ref": "#/components/schemas/GeneralError" } } } } }, "securitySchemes": { "api_key": { "type": "apiKey", "name": "api_key", "in": "header" }, "petstore_auth": { "type": "oauth2", "flows": { "implicit": { "authorizationUrl": "http://example.org/api/oauth/dialog", "scopes": { "write:pets": "modify pets in your account", "read:pets": "read your pets" } } } } } } ``` ```yaml components: schemas: GeneralError: type: object properties: code: type: integer format: int32 message: type: string Category: type: object properties: id: type: integer format: int64 name: type: string Tag: type: object properties: id: type: integer format: int64 name: type: string parameters: skipParam: name: skip in: query description: number of items to skip required: true schema: type: integer format: int32 limitParam: name: limit in: query description: max records to return required: true schema: type: integer format: int32 responses: NotFound: description: Entity not found. IllegalInput: description: Illegal input for operation. GeneralError: description: General Error content: application/json: schema: $ref: '#/components/schemas/GeneralError' securitySchemes: api_key: type: apiKey name: api_key in: header petstore_auth: type: oauth2 flows: implicit: authorizationUrl: http://example.org/api/oauth/dialog scopes: write:pets: modify pets in your account read:pets: read your pets ``` Holds the relative paths to the individual endpoints and their operations. The path is appended to the URL from the in order to construct the full URL. The Paths MAY be empty, due to . Field Pattern | Type | Description |::| <a name="pathsPath"></a>/{path} | | A relative path to an individual endpoint. The field name MUST begin with a slash. The path is appended (no relative URL resolution) to the expanded URL from the 's `url` field in order to construct the full URL. is allowed. When matching URLs, concrete (non-templated) paths would be matched before their templated counterparts. Templated paths with the same hierarchy but different templated names MUST NOT exist as they are identical. In case of ambiguous matching, it's up to the tooling to decide which one to use. This object MAY be extended with . Assuming the following paths, the concrete definition, `/pets/mine`, will be matched first if used: ``` /pets/{petId} /pets/mine ``` The following paths are considered identical and invalid: ``` /pets/{petId} /pets/{name} ``` The following may lead to ambiguous resolution: ``` /{entity}/me /books/{id} ``` ```json { "/pets": { "get": { "description": "Returns all pets from the system that the user has access to", "responses": { "200": { "description": "A list of pets.", "content": { "application/json": { "schema": { "type": "array", "items": { "$ref": "#/components/schemas/pet" } } } } } } } } } ``` ```yaml /pets: get: description: Returns all pets from the system that the user has access to responses: '200': description: A list of pets. content: application/json: schema: type: array items:

'#/components/schemas/pet' ``` Describes the operations available on a single path. A Path Item MAY be empty, due to . The path itself is still exposed to the documentation viewer but they will not know which operations and parameters are available. Field Name | Type | Description |::| <a name="pathItemRef"></a>$ref | `string` | Allows for an external definition of this path item. The referenced structure MUST be in the format of a . If there are conflicts between the referenced definition and this Path Item's definition, the behavior is undefined. <a name="pathItemSummary"></a>summary| `string` | An optional, string summary, intended to apply to all operations in this path. <a name="pathItemDescription"></a>description | `string` | An optional, string description, intended to apply to all operations in this path. MAY be used for rich text representation. <a name="pathItemGet"></a>get | | A definition of a GET operation on this path. <a name="pathItemPut"></a>put | | A definition of a PUT operation on this path. <a name="pathItemPost"></a>post | | A definition of a POST operation on this path. <a name="pathItemDelete"></a>delete | | A definition of a DELETE operation on this path. <a name="pathItemOptions"></a>options | | A definition of a OPTIONS operation on this path. <a name="pathItemHead"></a>head | | A definition of a HEAD operation on this path. <a name="pathItemPatch"></a>patch | | A definition of a PATCH operation on this path. <a name="pathItemTrace"></a>trace | | A definition of a TRACE operation on this path. <a name="pathItemServers"></a>servers | ] | An alternative `server` array to service all operations in this path. <a name="pathItemParameters"></a>parameters | \| ] | A list of parameters that are applicable for all the operations described under this path. These parameters can be overridden at the operation level, but cannot be removed there. The list MUST NOT include duplicated parameters. A unique parameter is defined by a combination of a and . The list can use the to link to parameters that are defined at the . This object MAY be extended with . ```json { "get": { "description": "Returns pets based on ID", "summary": "Find pets by ID", "operationId": "getPetsById", "responses": { "200": { "description": "pet response", "content": { "/": { "schema": { "type": "array", "items": { "$ref": "#/components/schemas/Pet" } } } } }, "default": { "description": "error payload", "content": { "text/html": { "schema": { "$ref": "#/components/schemas/ErrorModel" } } } } } }, "parameters": [ { "name": "id", "in": "path", "description": "ID of pet to use", "required": true, "schema": { "type": "array", "items": { "type": "string" } }, "style": "simple" } ] } ``` ```yaml get: description: Returns pets based on ID summary: Find pets by ID operationId: getPetsById responses: '200': description: pet response content: '/' : schema: type: array items: $ref: '#/components/schemas/Pet' default: description: error payload content: 'text/html': schema: $ref: '#/components/schemas/ErrorModel' parameters: name: id in: path description: ID of pet to use required: true schema: type: array style: simple items: type: string ``` Describes a single API operation on a path. Field Name | Type | Description |::| <a name="operationTags"></a>tags | [`string`] | A list of tags for API documentation control. Tags can be used for logical grouping of operations by resources or any other qualifier. <a name="operationSummary"></a>summary | `string` | A short summary of what the operation does. <a name="operationDescription"></a>description | `string` | A verbose explanation of the operation behavior. MAY be used for rich text representation. <a name="operationExternalDocs"></a>externalDocs | | Additional external documentation for this operation. <a name="operationId"></a>operationId | `string` | Unique string used to identify the

The id MUST be unique among all operations described in the API. The operationId value is case-sensitive. Tools and libraries MAY use the operationId to uniquely identify an operation, therefore, it is RECOMMENDED to follow common programming naming conventions. <a name="operationParameters"></a>parameters | \| ] | A list of parameters that are applicable for this operation. If a parameter is already defined at the , the new definition will override it but can never remove it. The list MUST NOT include duplicated parameters. A unique parameter is defined by a combination of a and . The list can use the to link to parameters that are defined at the . <a name="operationRequestBody"></a>requestBody | \| | The request body applicable for this operation. The `requestBody` is only supported in HTTP methods where the HTTP 1.1 specification has explicitly defined semantics for request bodies. In other cases where the HTTP spec is vague, `requestBody` SHALL be ignored by consumers. <a name="operationResponses"></a>responses | | REQUIRED. The list of possible responses as they are returned from executing this operation. <a name="operationCallbacks"></a>callbacks | Map \| ] | A map of possible out-of band callbacks related to the parent operation. The key is a unique identifier for the Callback Object. Each value in the map is a that describes a request that may be initiated by the API provider and the expected responses. The key value used to identify the callback object is an expression, evaluated at runtime, that identifies a URL to use for the callback operation. <a name="operationDeprecated"></a>deprecated | `boolean` | Declares this operation to be deprecated. Consumers SHOULD refrain from usage of the declared operation. Default value is `false`. <a name="operationSecurity"></a>security | ] | A declaration of which security mechanisms can be used for this operation. The list of values includes alternative security requirement objects that can be used. Only one of the security requirement objects need to be satisfied to authorize a request. This definition overrides any declared top-level . To remove a top-level security declaration, an empty array can be used. <a name="operationServers"></a>servers | ] | An alternative `server` array to service this operation. If an alternative `server` object is specified at the Path Item Object or Root level, it will be overridden by this value. This object MAY be extended with . ```json { "tags": [ "pet" ], "summary": "Updates a pet in the store with form data", "operationId": "updatePetWithForm", "parameters": [ { "name": "petId", "in": "path", "description": "ID of pet that needs to be updated", "required": true, "schema": { "type": "string" } } ], "requestBody": { "content": { "application/x-www-form-urlencoded": { "schema": { "type": "object", "properties": { "name": { "description": "Updated name of the pet", "type": "string" }, "status": { "description": "Updated status of the pet", "type": "string" } }, "required": ["status"] } } } }, "responses": { "200": { "description": "Pet updated.", "content": { "application/json": {}, "application/xml": {} } }, "405": { "description": "Method Not Allowed", "content": { "application/json": {}, "application/xml": {} } } }, "security": [ { "petstore_auth": [ "write:pets", "read:pets" ] } ] } ``` ```yaml tags: pet summary: Updates a pet in the store with form data operationId: updatePetWithForm parameters: name: petId in: path description: ID of pet that needs to be updated required: true schema: type: string requestBody: content: 'application/x-www-form-urlencoded': schema: properties: name: description: Updated name of the pet type: string status: description: Updated status of the pet type: string required: status responses: '200': description: Pet

content: 'application/json': {} 'application/xml': {} '405': description: Method Not Allowed content: 'application/json': {} 'application/xml': {} security: petstore_auth: write:pets read:pets ``` Allows referencing an external resource for extended documentation. Field Name | Type | Description |::| <a name="externalDocDescription"></a>description | `string` | A short description of the target documentation. MAY be used for rich text representation. <a name="externalDocUrl"></a>url | `string` | REQUIRED. The URL for the target documentation. Value MUST be in the format of a URL. This object MAY be extended with . ```json { "description": "Find more info here", "url": "https://example.com" } ``` ```yaml description: Find more info here url: https://example.com ``` Describes a single operation parameter. A unique parameter is defined by a combination of a and . There are four possible parameter locations specified by the `in` field: path - Used together with , where the parameter value is actually part of the operation's URL. This does not include the host or base path of the API. For example, in `/items/{itemId}`, the path parameter is `itemId`. query - Parameters that are appended to the URL. For example, in `/items?id=###`, the query parameter is `id`. header - Custom headers that are expected as part of the request. Note that states header names are case insensitive. cookie - Used to pass a specific cookie value to the API. Field Name | Type | Description |::| <a name="parameterName"></a>name | `string` | REQUIRED. The name of the parameter. Parameter names are case sensitive. <ul><li>If is `"path"`, the `name` field MUST correspond to the associated path segment from the field in the . See for further information.<li>If is `"header"` and the `name` field is `"Accept"`, `"Content-Type"` or `"Authorization"`, the parameter definition SHALL be ignored.<li>For all other cases, the `name` corresponds to the parameter name used by the property.</ul> <a name="parameterIn"></a>in | `string` | REQUIRED. The location of the parameter. Possible values are "query", "header", "path" or "cookie". <a name="parameterDescription"></a>description | `string` | A brief description of the parameter. This could contain examples of use. MAY be used for rich text representation. <a name="parameterRequired"></a>required | `boolean` | Determines whether this parameter is mandatory. If the is "path", this property is REQUIRED and its value MUST be `true`. Otherwise, the property MAY be included and its default value is `false`. <a name="parameterDeprecated"></a> deprecated | `boolean` | Specifies that a parameter is deprecated and SHOULD be transitioned out of usage. Default value is `false`. <a name="parameterAllowEmptyValue"></a> allowEmptyValue | `boolean` | Sets the ability to pass empty-valued parameters. This is valid only for `query` parameters and allows sending a parameter with an empty value. Default value is `false`. If is used, and if behavior is `n/a` (cannot be serialized), the value of `allowEmptyValue` SHALL be ignored. Use of this property is NOT RECOMMENDED, as it is likely to be removed in a later revision. The rules for serialization of the parameter are specified in one of two ways. For simpler scenarios, a and can describe the structure and syntax of the parameter. Field Name | Type | Description |::| <a name="parameterStyle"></a>style | `string` | Describes how the parameter value will be serialized depending on the type of the parameter value. Default values (based on value of `in`): for `query` - `form`; for `path` - `simple`; for `header` - `simple`; for `cookie` - `form`. <a name="parameterExplode"></a>explode | `boolean` | When this is true, parameter values of type `array` or `object` generate separate parameters for each value of the array or key-value pair of the map. For other types of parameters this property has no effect. When is `form`, the default value is

For all other styles, the default value is `false`. <a name="parameterAllowReserved"></a>allowReserved | `boolean` | Determines whether the parameter value SHOULD allow reserved characters, as defined by `:/?#[]@!$&'()*+,;=` to be included without percent-encoding. This property only applies to parameters with an `in` value of `query`. The default value is `false`. <a name="parameterSchema"></a>schema | \| | The schema defining the type used for the parameter. <a name="parameterExample"></a>example | Any | Example of the media type. The example SHOULD match the specified schema and encoding properties if present. The `example` field is mutually exclusive of the `examples` field. Furthermore, if referencing a `schema` which contains an example, the `example` value SHALL override the example provided by the schema. To represent examples of media types that cannot naturally be represented in JSON or YAML, a string value can contain the example with escaping where necessary. <a name="parameterExamples"></a>examples | Map \| ] | Examples of the media type. Each example SHOULD contain a value in the correct format as specified in the parameter encoding. The `examples` field is mutually exclusive of the `example` field. Furthermore, if referencing a `schema` which contains an example, the `examples` value SHALL override the example provided by the schema. For more complex scenarios, the property can define the media type and schema of the parameter. A parameter MUST contain either a `schema` property, or a `content` property, but not both. When `example` or `examples` are provided in conjunction with the `schema` object, the example MUST follow the prescribed serialization strategy for the parameter. Field Name | Type | Description |::| <a name="parameterContent"></a>content | Map] | A map containing the representations for the parameter. The key is the media type and the value describes it. The map MUST only contain one entry. In order to support common ways of serializing simple parameters, a set of `style` values are defined. `style` | | `in` | Comments -- | | -- | -- matrix | `primitive`, `array`, `object` | `path` | Path-style parameters defined by label | `primitive`, `array`, `object` | `path` | Label style parameters defined by form | `primitive`, `array`, `object` | `query`, `cookie` | Form style parameters defined by . This option replaces `collectionFormat` with a `csv` (when `explode` is false) or `multi` (when `explode` is true) value from OpenAPI 2.0. simple | `array` | `path`, `header` | Simple style parameters defined by . This option replaces `collectionFormat` with a `csv` value from OpenAPI 2.0. spaceDelimited | `array` | `query` | Space separated array values. This option replaces `collectionFormat` equal to `ssv` from OpenAPI 2.0. pipeDelimited | `array` | `query` | Pipe separated array values. This option replaces `collectionFormat` equal to `pipes` from OpenAPI 2.0. deepObject | `object` | `query` | Provides a simple way of rendering nested objects using form parameters. Assume a parameter named `color` has one of the following values: ``` string -> "blue" array -> ["blue","black","brown"] object -> { "R": 100, "G": 200, "B": 150 } ``` The following table shows examples of rendering differences for each value. | `explode` | `empty` | `string` | `array` | `object` -- | | -- | -- | --|- matrix | false | ;color | ;color=blue | ;color=blue,black,brown | ;color=R,100,G,200,B,150 matrix | true | ;color | ;color=blue | ;color=blue;color=black;color=brown | ;R=100;G=200;B=150 label | false | . | .blue | .blue.black.brown | .R.100.G.200.B.150 label | true | . | .blue | .blue.black.brown |

form | false | color= | color=blue | color=blue,black,brown | color=R,100,G,200,B,150 form | true | color= | color=blue | color=blue&color=black&color=brown | R=100&G=200&B=150 simple | false | n/a | blue | blue,black,brown | R,100,G,200,B,150 simple | true | n/a | blue | blue,black,brown | R=100,G=200,B=150 spaceDelimited | false | n/a | n/a | blue%20black%20brown | R%20100%20G%20200%20B%20150 pipeDelimited | false | n/a | n/a | blue\|black\|brown | R\|100\|G\|200|G\|150 deepObject | true | n/a | n/a | n/a | color[R]=100&color[G]=200&color[B]=150 This object MAY be extended with . A header parameter with an array of 64 bit integer numbers: ```json { "name": "token", "in": "header", "description": "token to be passed as a header", "required": true, "schema": { "type": "array", "items": { "type": "integer", "format": "int64" } }, "style": "simple" } ``` ```yaml name: token in: header description: token to be passed as a header required: true schema: type: array items: type: integer format: int64 style: simple ``` A path parameter of a string value: ```json { "name": "username", "in": "path", "description": "username to fetch", "required": true, "schema": { "type": "string" } } ``` ```yaml name: username in: path description: username to fetch required: true schema: type: string ``` An optional query parameter of a string value, allowing multiple values by repeating the query parameter: ```json { "name": "id", "in": "query", "description": "ID of the object to fetch", "required": false, "schema": { "type": "array", "items": { "type": "string" } }, "style": "form", "explode": true } ``` ```yaml name: id in: query description: ID of the object to fetch required: false schema: type: array items: type: string style: form explode: true ``` A free-form query parameter, allowing undefined parameters of a specific type: ```json { "in": "query", "name": "freeForm", "schema": { "type": "object", "additionalProperties": { "type": "integer" }, }, "style": "form" } ``` ```yaml in: query name: freeForm schema: type: object additionalProperties: type: integer style: form ``` A complex parameter using `content` to define serialization: ```json { "in": "query", "name": "coordinates", "content": { "application/json": { "schema": { "type": "object", "required": [ "lat", "long" ], "properties": { "lat": { "type": "number" }, "long": { "type": "number" } } } } } } ``` ```yaml in: query name: coordinates content: application/json: schema: type: object required: lat long properties: lat: type: number long: type: number ``` Describes a single request body. Field Name | Type | Description |::| <a name="requestBodyDescription"></a>description | `string` | A brief description of the request body. This could contain examples of use. MAY be used for rich text representation. <a name="requestBodyContent"></a>content | Map] | REQUIRED. The content of the request body. The key is a media type or and the value describes it. For requests that match multiple keys, only the most specific key is applicable. e.g. text/plain overrides text/* <a name="requestBodyRequired"></a>required | `boolean` | Determines if the request body is required in the request. Defaults to `false`. This object MAY be extended with . A request body with a referenced model definition. ```json { "description": "user to add to the system", "content": { "application/json": { "schema": { "$ref": "#/components/schemas/User" }, "examples": { "user" : { "summary": "User Example", "externalValue": "http://foo.bar/examples/user-example.json" } } }, "application/xml": { "schema": { "$ref": "#/components/schemas/User" }, "examples": { "user" : { "summary": "User example in XML", "externalValue": "http://foo.bar/examples/user-example.xml" } } }, "text/plain": { "examples": { "user" : { "summary": "User example in Plain text", "externalValue": "http://foo.bar/examples/user-example.txt" } } }, "/": { "examples": { "user" : { "summary": "User example in other format", "externalValue": "http://foo.bar/examples/user-example.whatever" } } } } } ``` ```yaml description: user to add to the system content: 'application/json': schema: $ref: '#/components/schemas/User' examples: user: summary: User Example externalValue:

'application/xml': schema: $ref: '#/components/schemas/User' examples: user: summary: User Example in XML externalValue: 'http://foo.bar/examples/user-example.xml' 'text/plain': examples: user: summary: User example in text plain format externalValue: 'http://foo.bar/examples/user-example.txt' '/': examples: user: summary: User example in other format externalValue: 'http://foo.bar/examples/user-example.whatever' ``` A body parameter that is an array of string values: ```json { "description": "user to add to the system", "content": { "text/plain": { "schema": { "type": "array", "items": { "type": "string" } } } } } ``` ```yaml description: user to add to the system required: true content: text/plain: schema: type: array items: type: string ``` Each Media Type Object provides schema and examples for the media type identified by its key. Field Name | Type | Description |::| <a name="mediaTypeSchema"></a>schema | \| | The schema defining the content of the request, response, or parameter. <a name="mediaTypeExample"></a>example | Any | Example of the media type. The example object SHOULD be in the correct format as specified by the media type. The `example` field is mutually exclusive of the `examples` field. Furthermore, if referencing a `schema` which contains an example, the `example` value SHALL override the example provided by the schema. <a name="mediaTypeExamples"></a>examples | Map \| ] | Examples of the media type. Each example object SHOULD match the media type and specified schema if present. The `examples` field is mutually exclusive of the `example` field. Furthermore, if referencing a `schema` which contains an example, the `examples` value SHALL override the example provided by the schema. <a name="mediaTypeEncoding"></a>encoding | Map] | A map between a property name and its encoding information. The key, being the property name, MUST exist in the schema as a property. The encoding object SHALL only apply to `requestBody` objects when the media type is `multipart` or `application/x-www-form-urlencoded`. This object MAY be extended with . ```json { "application/json": { "schema": { "$ref": "#/components/schemas/Pet" }, "examples": { "cat" : { "summary": "An example of a cat", "value": { "name": "Fluffy", "petType": "Cat", "color": "White", "gender": "male", "breed": "Persian" } }, "dog": { "summary": "An example of a dog with a cat's name", "value" : { "name": "Puma", "petType": "Dog", "color": "Black", "gender": "Female", "breed": "Mixed" }, "frog": { "$ref": "#/components/examples/frog-example" } } } } } ``` ```yaml application/json: schema: $ref: "#/components/schemas/Pet" examples: cat: summary: An example of a cat value: name: Fluffy petType: Cat color: White gender: male breed: Persian dog: summary: An example of a dog with a cat's name value: name: Puma petType: Dog color: Black gender: Female breed: Mixed frog: $ref: "#/components/examples/frog-example" ``` In contrast with the 2.0 specification, `file` input/output content in OpenAPI is described with the same semantics as any other schema type. Specifically: ```yaml schema: type: string format: base64 ``` ```yaml schema: type: string format: binary ``` These examples apply to either input payloads of file uploads or response

A `requestBody` for submitting a file in a `POST` operation may look like the following example: ```yaml requestBody: content: application/octet-stream: schema: type: string format: binary ``` In addition, specific media types MAY be specified: ```yaml requestBody: content: 'image/jpeg': schema: type: string format: binary 'image/png': schema: type: string format: binary ``` To upload multiple files, a `multipart` media type MUST be used: ```yaml requestBody: content: multipart/form-data: schema: properties: file: type: array items: type: string format: binary ``` To submit content using form url encoding via , the following definition may be used: ```yaml requestBody: content: application/x-www-form-urlencoded: schema: type: object properties: id: type: string format: uuid address: type: object properties: {} ``` In this example, the contents in the `requestBody` MUST be stringified per when passed to the server. In addition, the `address` field complex object will be stringified. When passing complex objects in the `application/x-www-form-urlencoded` content type, the default serialization strategy of such properties is described in the 's property as `form`. It is common to use `multipart/form-data` as a `Content-Type` when transferring request bodies to operations. In contrast to 2.0, a `schema` is REQUIRED to define the input parameters to the operation when using `multipart` content. This supports complex structures as well as supporting mechanisms for multiple file uploads. When passing in `multipart` types, boundaries MAY be used to separate sections of the content being transferred thus, the following default `Content-Type`s are defined for `multipart`: If the property is a primitive, or an array of primitive values, the default Content-Type is `text/plain` If the property is complex, or an array of complex values, the default Content-Type is `application/json` If the property is a `type: string` with `format: binary` or `format: base64` (aka a file object), the default Content-Type is `application/octet-stream` Examples: ```yaml requestBody: content: multipart/form-data: schema: type: object properties: id: type: string format: uuid address: type: object properties: {} profileImage: type: string format: binary children: type: array items: type: string addresses: type: array items: type: '#/components/schemas/Address' ``` An `encoding` attribute is introduced to give you control over the serialization of parts of `multipart` request bodies. This attribute is only applicable to `multipart` and `application/x-www-form-urlencoded` request bodies. A single encoding definition applied to a single schema property. Field Name | Type | Description |::| <a name="encodingContentType"></a>contentType | `string` | The Content-Type for encoding a specific property. Default value depends on the property type: for `string` with `format` being `binary` `application/octet-stream`; for other primitive types `text/plain`; for `object` - `application/json`; for `array` the default is defined based on the inner type. The value can be a specific media type (e.g. `application/json`), a wildcard media type (e.g. `image/*`), or a comma-separated list of the two types. <a name="encodingHeaders"></a>headers | Map \| ] | A map allowing additional information to be provided as headers, for example `Content-Disposition`. `Content-Type` is described separately and SHALL be ignored in this section. This property SHALL be ignored if the request body media type is not a `multipart`. <a name="encodingStyle"></a>style | `string` | Describes how a specific property value will be serialized depending on its type. See for details on the property. The behavior follows the same values as `query` parameters, including default values. This property SHALL be ignored if the request body media type is not `application/x-www-form-urlencoded`. <a name="encodingExplode"></a>explode | `boolean` | When this is true, property values of type `array` or `object` generate separate parameters for each value of the array, or key-value-pair of the map. For other types of properties this property has no effect. When is `form`, the default value is `true`. For all other styles, the default value is `false`. This property SHALL be ignored if the request body media type is not `application/x-www-form-urlencoded`. <a name="encodingAllowReserved"></a>allowReserved | `boolean` | Determines whether the parameter value SHOULD allow reserved characters, as defined by `:/?#[]@!$&'()*+,;=` to be included without percent-encoding. The default value is `false`. This property SHALL be ignored if the request body media type is not `application/x-www-form-urlencoded`. This object MAY be extended with

```yaml requestBody: content: multipart/mixed: schema: type: object properties: id: type: string format: uuid address: type: object properties: {} historyMetadata: description: metadata in XML format type: object properties: {} profileImage: type: string format: binary encoding: historyMetadata: contentType: application/xml; charset=utf-8 profileImage: contentType: image/png, image/jpeg headers: X-Rate-Limit-Limit: description: The number of allowed requests in the current period schema: type: integer ``` A container for the expected responses of an operation. The container maps a HTTP response code to the expected response. The documentation is not necessarily expected to cover all possible HTTP response codes because they may not be known in advance. However, documentation is expected to cover a successful operation response and any known errors. The `default` MAY be used as a default response object for all HTTP codes that are not covered individually by the specification. The `Responses Object` MUST contain at least one response code, and it SHOULD be the response for a successful operation call. Field Name | Type | Description |::| <a name="responsesDefault"></a>default | \| | The documentation of responses other than the ones declared for specific HTTP response codes. Use this field to cover undeclared responses. A can link to a response that the section defines. Field Pattern | Type | Description |::| <a name="responsesCode"></a> | \| | Any can be used as the property name, but only one property per code, to describe the expected response for that HTTP status code. A can link to a response that is defined in the section. This field MUST be enclosed in quotation marks (for example, "200") for compatibility between JSON and YAML. To define a range of response codes, this field MAY contain the uppercase wildcard character `X`. For example, `2XX` represents all response codes between `[200-299]`. Only the following range definitions are allowed: `1XX`, `2XX`, `3XX`, `4XX`, and `5XX`. If a response is defined using an explicit code, the explicit code definition takes precedence over the range definition for that code. This object MAY be extended with . A 200 response for a successful operation and a default response for others (implying an error): ```json { "200": { "description": "a pet to be returned", "content": { "application/json": { "schema": { "$ref": "#/components/schemas/Pet" } } } }, "default": { "description": "Unexpected error", "content": { "application/json": { "schema": { "$ref": "#/components/schemas/ErrorModel" } } } } } ``` ```yaml '200': description: a pet to be returned content: application/json: schema: $ref: '#/components/schemas/Pet' default: description: Unexpected error content: application/json: schema: $ref: '#/components/schemas/ErrorModel' ``` Describes a single response from an API Operation, including design-time, static `links` to operations based on the response. Field Name | Type | Description |::| <a name="responseDescription"></a>description | `string` | REQUIRED. A short description of the response. MAY be used for rich text representation. <a name="responseHeaders"></a>headers | Map \| ] | Maps a header name to its definition. states header names are case insensitive. If a response header is defined with the name `"Content-Type"`, it SHALL be ignored. <a name="responseContent"></a>content | Map] | A map containing descriptions of potential response payloads. The key is a media type or and the value describes it. For responses that match multiple keys, only the most specific key is applicable. e.g. text/plain overrides text/* <a name="responseLinks"></a>links | Map \| ] | A map of operations links that can be followed from the response. The key of the map is a short name for the link, following the naming constraints of the names for . This object MAY be extended with . Response of an array of a complex type: ```json { "description": "A complex object array response", "content": { "application/json": { "schema": { "type": "array", "items": {

"#/components/schemas/VeryComplexType" } } } } } ``` ```yaml description: A complex object array response content: application/json: schema: type: array items: $ref: '#/components/schemas/VeryComplexType' ``` Response with a string type: ```json { "description": "A simple string response", "content": { "text/plain": { "schema": { "type": "string" } } } } ``` ```yaml description: A simple string response content: text/plain: schema: type: string ``` Plain text response with headers: ```json { "description": "A simple string response", "content": { "text/plain": { "schema": { "type": "string" } } }, "headers": { "X-Rate-Limit-Limit": { "description": "The number of allowed requests in the current period", "schema": { "type": "integer" } }, "X-Rate-Limit-Remaining": { "description": "The number of remaining requests in the current period", "schema": { "type": "integer" } }, "X-Rate-Limit-Reset": { "description": "The number of seconds left in the current period", "schema": { "type": "integer" } } } } ``` ```yaml description: A simple string response content: text/plain: schema: type: string example: 'whoa!' headers: X-Rate-Limit-Limit: description: The number of allowed requests in the current period schema: type: integer X-Rate-Limit-Remaining: description: The number of remaining requests in the current period schema: type: integer X-Rate-Limit-Reset: description: The number of seconds left in the current period schema: type: integer ``` Response with no return value: ```json { "description": "object created" } ``` ```yaml description: object created ``` A map of possible out-of band callbacks related to the parent operation. Each value in the map is a that describes a set of requests that may be initiated by the API provider and the expected responses. The key value used to identify the callback object is an expression, evaluated at runtime, that identifies a URL to use for the callback operation. Field Pattern | Type | Description |::| <a name="callbackExpression"></a>{expression} | | A Path Item Object used to define a callback request and expected responses. A is available. This object MAY be extended with . The key that identifies the is a that can be evaluated in the context of a runtime HTTP request/response to identify the URL to be used for the callback request. A simple example might be `$request.body#/url`. However, using a the complete HTTP message can be accessed. This includes accessing any part of a body that a JSON Pointer can reference. For example, given the following HTTP request: ```http POST /subscribe/myevent?queryUrl=http://clientdomain.com/stillrunning HTTP/1.1 Host: example.org Content-Type: application/json Content-Length: 187 { "failedUrl" : "http://clientdomain.com/failed", "successUrls" : [ "http://clientdomain.com/fast", "http://clientdomain.com/medium", "http://clientdomain.com/slow" ] } 201 Created Location: http://example.org/subscription/1 ``` The following examples show how the various expressions evaluate, assuming the callback operation has a path parameter named `eventType` and a query parameter named `queryUrl`. Expression | Value |: $url | http://example.org/subscribe/myevent?queryUrl=http://clientdomain.com/stillrunning $method | POST $request.path.eventType | myevent $request.query.queryUrl | http://clientdomain.com/stillrunning $request.header.content-Type | application/json $request.body#/failedUrl | http://clientdomain.com/failed $request.body#/successUrls/2 | http://clientdomain.com/medium $response.header.Location | http://example.org/subscription/1 The following example shows a callback to the URL specified by the `id` and `email` property in the request body. ```yaml myWebhook: 'http://notificationServer.com?transactionId={$request.body#/id}&email={$request.body#/email}': post: requestBody: description: Callback payload content: 'application/json': schema: $ref: '#/components/schemas/SomePayload' responses: '200': description: webhook successfully processed and no retries will be performed ``` Field Name | Type | Description |::| <a name="exampleSummary"></a>summary | `string` | Short description for the example. <a name="exampleDescription"></a>description | `string` | Long description for the example. MAY be used for rich text representation. <a name="exampleValue"></a>value | Any | Embedded literal example. The `value` field and `externalValue` field are mutually exclusive. To represent examples of media types that cannot naturally represented in JSON or YAML, use a string value to contain the example, escaping where necessary. <a name="exampleExternalValue"></a>externalValue | `string` | A URL that points to the literal

This provides the capability to reference examples that cannot easily be included in JSON or YAML documents. The `value` field and `externalValue` field are mutually exclusive. This object MAY be extended with . In all cases, the example value is expected to be compatible with the type schema of its associated value. Tooling implementations MAY choose to validate compatibility automatically, and reject the example value(s) if incompatible. In a model: ```yaml schemas: properties: name: type: string examples: name: $ref: http://example.org/petapi-examples/openapi.json#/components/examples/name-example ``` In a request body: ```yaml requestBody: content: 'application/json': schema: $ref: '#/components/schemas/Address' examples: foo: summary: A foo example value: {"foo": "bar"} bar: summary: A bar example value: {"bar": "baz"} 'application/xml': examples: xmlExample: summary: This is an example in XML externalValue: 'http://example.org/examples/address-example.xml' 'text/plain': examples: textExample: summary: This is a text example externalValue: 'http://foo.bar/examples/address-example.txt' ``` In a parameter: ```yaml parameters: name: 'zipCode' in: 'query' schema: type: 'string' format: 'zip-code' examples: zip-example: $ref: '#/components/examples/zip-example' ``` In a response: ```yaml responses: '200': description: your car appointment has been booked content: application/json: schema: $ref: '#/components/schemas/SuccessResponse' examples: confirmation-success: $ref: '#/components/examples/confirmation-success' ``` The `Link object` represents a possible design-time link for a response. The presence of a link does not guarantee the caller's ability to successfully invoke it, rather it provides a known relationship and traversal mechanism between responses and other operations. Unlike dynamic links (i.e. links provided in the response payload), the OAS linking mechanism does not require link information in the runtime response. For computing links, and providing instructions to execute them, a is used for accessing values in an operation and using them as parameters while invoking the linked operation. Field Name | Type | Description |::| <a name="linkOperationRef"></a>operationRef | `string` | A relative or absolute reference to an OAS operation. This field is mutually exclusive of the `operationId` field, and MUST point to an . Relative `operationRef` values MAY be used to locate an existing in the OpenAPI definition. <a name="linkOperationId"></a>operationId | `string` | The name of an existing, resolvable OAS operation, as defined with a unique `operationId`. This field is mutually exclusive of the `operationRef` field. <a name="linkParameters"></a>parameters | Map] | A map representing parameters to pass to an operation as specified with `operationId` or identified via `operationRef`. The key is the parameter name to be used, whereas the value can be a constant or an expression to be evaluated and passed to the linked operation. The parameter name can be qualified using the `[{in}.]{name}` for operations that use the same parameter name in different locations (e.g. path.id). <a name="linkRequestBody"></a>requestBody | Any \| | A literal value or to use as a request body when calling the target operation. <a name="linkDescription"></a>description | `string` | A description of the link. MAY be used for rich text representation. <a name="linkServer"></a>server | | A server object to be used by the target operation. This object MAY be extended with . A linked operation MUST be identified using either an `operationRef` or `operationId`. In the case of an `operationId`, it MUST be unique and resolved in the scope of the OAS document. Because of the potential for name clashes, the `operationRef` syntax is preferred for specifications with external references. Computing a link from a request operation where the `$request.path.id` is used to pass a request parameter to the linked operation. ```yaml paths: /users/{id}: parameters: name: id in: path required: true description: the user identifier, as userId schema: type: string get: responses: '200': description: the user being returned content: application/json: schema: type: object properties:

# the unique user id type: string format: uuid links: address: operationId: getUserAddress parameters: userId: $request.path.id /users/{userid}/address: parameters: name: userid in: path required: true description: the user identifier, as userId schema: type: string get: operationId: getUserAddress responses: '200': description: the user's address ``` When a runtime expression fails to evaluate, no parameter value is passed to the target operation. Values from the response body can be used to drive a linked operation. ```yaml links: address: operationId: getUserAddressByUUID parameters: userUuid: $response.body#/uuid ``` Clients follow all links at their discretion. Neither permissions, nor the capability to make a successful call to that link, is guaranteed solely by the existence of a relationship. As references to `operationId` MAY NOT be possible (the `operationId` is an optional value), references MAY also be made through a relative `operationRef`: ```yaml links: UserRepositories: operationRef: '#/paths/~12.0~1repositories~1{username}/get' parameters: username: $response.body#/username ``` or an absolute `operationRef`: ```yaml links: UserRepositories: operationRef: 'https://na2.gigantic-server.com/#/paths/~12.0~1repositories~1{username}/get' parameters: username: $response.body#/username ``` Note that in the use of `operationRef`, the escaped forward-slash is necessary when using JSON references. Runtime expressions allow defining values based on information that will only be available within the HTTP message in an actual API call. This mechanism is used by and . The runtime expression is defined by the following syntax ``` expression = ( "$url" | "$method" | "$statusCode" | "$request." source | "$response." source ) source = ( header-reference | query-reference | path-reference | body-reference ) header-reference = "header." token query-reference = "query." name path-reference = "path." name body-reference = "body" ["#" fragment] fragment = a JSON Pointer name = *( char ) char = as per RFC token = as per RFC ``` The `name` identifier is case-sensitive, whereas `token` is not. The table below provides examples of runtime expressions and examples of their use in a value: Source Location | example expression | notes |:|:| HTTP Method | `$method` | The allowable values for the `$method` will be those for the HTTP operation. Requested media type | `$request.header.accept` | Request parameter | `$request.path.id` | Request parameters MUST be declared in the `parameters` section of the parent operation or they cannot be evaluated. This includes request headers. Request body property | `$request.body#/user/uuid` | In operations which accept payloads, references may be made to portions of the `requestBody` or the entire body. Request URL | `$url` | Response value | `$response.body#/status` | In operations which return payloads, references may be made to portions of the response body or the entire body. Response header | `$response.header.Server` | Single header values only are available Runtime expressions preserve the type of the referenced value. Expressions can be embedded into string values by surrounding the expression with `{}` curly braces. The Header Object follows the structure of the with the following changes: `name` MUST NOT be specified, it is given in the corresponding `headers` map. `in` MUST NOT be specified, it is implicitly in `header`. All traits that are affected by the location MUST be applicable to a location of `header` (for example, ). A simple header of type `integer`: ```json { "description": "The number of allowed requests in the current period", "schema": { "type": "integer" } } ``` ```yaml description: The number of allowed requests in the current period schema: type: integer ``` Adds metadata to a single tag that is used by the . It is not mandatory to have a Tag Object per tag defined in the Operation Object instances. Field Name | Type | Description |::| <a name="tagName"></a>name | `string` |

The name of the tag. <a name="tagDescription"></a>description | `string` | A short description for the tag. MAY be used for rich text representation. <a name="tagExternalDocs"></a>externalDocs | | Additional external documentation for this tag. This object MAY be extended with . ```json { "name": "pet", "description": "Pets operations" } ``` ```yaml name: pet description: Pets operations ``` A simple object to allow referencing other components in the specification, internally and externally. The Reference Object is defined by and follows the same structure, behavior and rules. For this specification, reference resolution is accomplished as defined by the JSON Reference specification and not by the JSON Schema specification. Field Name | Type | Description |::| <a name="referenceRef"></a>$ref | `string` | REQUIRED. The reference string. This object cannot be extended with additional properties and any properties added SHALL be ignored. ```json { "$ref": "#/components/schemas/Pet" } ``` ```yaml $ref: '#/components/schemas/Pet' ``` ```json { "$ref": "Pet.json" } ``` ```yaml $ref: Pet.yaml ``` ```json { "$ref": "definitions.json#/Pet" } ``` ```yaml $ref: definitions.yaml#/Pet ``` The Schema Object allows the definition of input and output data types. These types can be objects, but also primitives and arrays. This object is an extended subset of the . For more information about the properties, see and . Unless stated otherwise, the property definitions follow the JSON Schema. The following properties are taken directly from the JSON Schema definition and follow the same specifications: title multipleOf maximum exclusiveMaximum minimum exclusiveMinimum maxLength minLength pattern (This string SHOULD be a valid regular expression, according to the dialect) maxItems minItems uniqueItems maxProperties minProperties required enum The following properties are taken from the JSON Schema definition but their definitions were adjusted to the OpenAPI Specification. type - Value MUST be a string. Multiple types via an array are not supported. allOf - Inline or referenced schema MUST be of a and not a standard JSON Schema. oneOf - Inline or referenced schema MUST be of a and not a standard JSON Schema. anyOf - Inline or referenced schema MUST be of a and not a standard JSON Schema. not - Inline or referenced schema MUST be of a and not a standard JSON Schema. items - Value MUST be an object and not an array. Inline or referenced schema MUST be of a and not a standard JSON Schema. `items` MUST be present if the `type` is `array`. properties - Property definitions MUST be a and not a standard JSON Schema (inline or referenced). additionalProperties - Value can be boolean or object. Inline or referenced schema MUST be of a and not a standard JSON Schema. Consistent with JSON Schema, `additionalProperties` defaults to `true`. description - MAY be used for rich text representation. format - See for further details. While relying on JSON Schema's defined formats, the OAS offers a few additional predefined formats. default - The default value represents what would be assumed by the consumer of the input as the value of the schema if one is not provided. Unlike JSON Schema, the value MUST conform to the defined type for the Schema Object defined at the same level. For example, if `type` is `string`, then `default` can be `"foo"` but cannot be `1`. Alternatively, any time a Schema Object can be used, a can be used in its place. This allows referencing definitions instead of defining them inline. Additional properties defined by the JSON Schema specification that are not mentioned here are strictly

Other than the JSON Schema subset fields, the following fields MAY be used for further schema documentation: Field Name | Type | Description |::| <a name="schemaNullable"></a>nullable | `boolean` | Allows sending a `null` value for the defined schema. Default value is `false`. <a name="schemaDiscriminator"></a>discriminator | | Adds support for polymorphism. The discriminator is an object name that is used to differentiate between other schemas which may satisfy the payload description. See for more details. <a name="schemaReadOnly"></a>readOnly | `boolean` | Relevant only for Schema `"properties"` definitions. Declares the property as "read only". This means that it MAY be sent as part of a response but SHOULD NOT be sent as part of the request. If the property is marked as `readOnly` being `true` and is in the `required` list, the `required` will take effect on the response only. A property MUST NOT be marked as both `readOnly` and `writeOnly` being `true`. Default value is `false`. <a name="schemaWriteOnly"></a>writeOnly | `boolean` | Relevant only for Schema `"properties"` definitions. Declares the property as "write only". Therefore, it MAY be sent as part of a request but SHOULD NOT be sent as part of the response. If the property is marked as `writeOnly` being `true` and is in the `required` list, the `required` will take effect on the request only. A property MUST NOT be marked as both `readOnly` and `writeOnly` being `true`. Default value is `false`. <a name="schemaXml"></a>xml | | This MAY be used only on properties schemas. It has no effect on root schemas. Adds additional metadata to describe the XML representation of this property. <a name="schemaExternalDocs"></a>externalDocs | | Additional external documentation for this schema. <a name="schemaExample"></a>example | Any | A free-form property to include an example of an instance for this schema. To represent examples that cannot be naturally represented in JSON or YAML, a string value can be used to contain the example with escaping where necessary. <a name="schemaDeprecated"></a> deprecated | `boolean` | Specifies that a schema is deprecated and SHOULD be transitioned out of usage. Default value is `false`. This object MAY be extended with . The OpenAPI Specification allows combining and extending model definitions using the `allOf` property of JSON Schema, in effect offering model composition. `allOf` takes an array of object definitions that are validated independently but together compose a single object. While composition offers model extensibility, it does not imply a hierarchy between the models. To support polymorphism, the OpenAPI Specification adds the `discriminator` field. When used, the `discriminator` will be the name of the property that decides which schema definition validates the structure of the model. As such, the `discriminator` field MUST be a required field. There are two ways to define the value of a discriminator for an inheriting instance. Use the schema name. Override the schema name by overriding the property with a new value. If a new value exists, this takes precedence over the schema name. As such, inline schema definitions, which do not have a given id, cannot be used in polymorphism. The property allows extra definitions when translating the JSON definition to XML. The contains additional information about the available options. ```json { "type": "string", "format": "email" } ``` ```yaml type: string format: email ``` ```json { "type": "object", "required": [ "name" ], "properties": { "name": { "type": "string" }, "address": { "$ref": "#/components/schemas/Address" }, "age": { "type": "integer", "format": "int32", "minimum": 0 } } } ``` ```yaml type: object required: name properties: name: type: string address:

'#/components/schemas/Address' age: type: integer format: int32 minimum: 0 ``` For a simple string to string mapping: ```json { "type": "object", "additionalProperties": { "type": "string" } } ``` ```yaml type: object additionalProperties: type: string ``` For a string to model mapping: ```json { "type": "object", "additionalProperties": { "$ref": "#/components/schemas/ComplexModel" } } ``` ```yaml type: object additionalProperties: $ref: '#/components/schemas/ComplexModel' ``` ```json { "type": "object", "properties": { "id": { "type": "integer", "format": "int64" }, "name": { "type": "string" } }, "required": [ "name" ], "example": { "name": "Puma", "id": 1 } } ``` ```yaml type: object properties: id: type: integer format: int64 name: type: string required: name example: name: Puma id: 1 ``` ```json { "components": { "schemas": { "ErrorModel": { "type": "object", "required": [ "message", "code" ], "properties": { "message": { "type": "string" }, "code": { "type": "integer", "minimum": 100, "maximum": 600 } } }, "ExtendedErrorModel": { "allOf": [ { "$ref": "#/components/schemas/ErrorModel" }, { "type": "object", "required": [ "rootCause" ], "properties": { "rootCause": { "type": "string" } } } ] } } } } ``` ```yaml components: schemas: ErrorModel: type: object required: message code properties: message: type: string code: type: integer minimum: 100 maximum: 600 ExtendedErrorModel: allOf: $ref: '#/components/schemas/ErrorModel' type: object required: rootCause properties: rootCause: type: string ``` ```json { "components": { "schemas": { "Pet": { "type": "object", "discriminator": { "propertyName": "petType" }, "properties": { "name": { "type": "string" }, "petType": { "type": "string" } }, "required": [ "name", "petType" ] }, "Cat": { "description": "A representation of a cat. Note that `Cat` will be used as the discriminator value.", "allOf": [ { "$ref": "#/components/schemas/Pet" }, { "type": "object", "properties": { "huntingSkill": { "type": "string", "description": "The measured skill for hunting", "default": "lazy", "enum": [ "clueless", "lazy", "adventurous", "aggressive" ] } }, "required": [ "huntingSkill" ] } ] }, "Dog": { "description": "A representation of a dog. Note that `Dog` will be used as the discriminator value.", "allOf": [ { "$ref": "#/components/schemas/Pet" }, { "type": "object", "properties": { "packSize": { "type": "integer", "format": "int32", "description": "the size of the pack the dog is from", "default": 0, "minimum": 0 } }, "required": [ "packSize" ] } ] } } } } ``` ```yaml components: schemas: Pet: type: object discriminator: propertyName: petType properties: name: type: string petType: type: string required: name petType Cat: ## "Cat" will be used as the discriminator value description: A representation of a cat allOf: $ref: '#/components/schemas/Pet' type: object properties: huntingSkill: type: string description: The measured skill for hunting enum: clueless lazy adventurous aggressive required: huntingSkill Dog: ## "Dog" will be used as the discriminator value description: A representation of a dog allOf: $ref: '#/components/schemas/Pet' type: object properties: packSize: type: integer format: int32 description: the size of the pack the dog is from default: 0 minimum: 0 required: packSize ``` When request bodies or response payloads may be one of a number of different schemas, a `discriminator` object can be used to aid in serialization, deserialization, and validation. The discriminator is a specific object in a schema which is used to inform the consumer of the specification of an alternative schema based on the value associated with it. When using the discriminator, inline schemas will not be considered. Field Name | Type | Description |::| <a name="propertyName"></a>propertyName | `string` | REQUIRED. The name of the property in the payload that will hold the discriminator value. <a name="discriminatorMapping"></a> mapping | Map[`string`, `string`] | An object to hold mappings between payload values and schema names or references. The discriminator object is legal only when using one of the composite keywords `oneOf`, `anyOf`, `allOf`. In OAS

a response payload MAY be described to be exactly one of any number of types: ```yaml MyResponseType: oneOf: $ref: '#/components/schemas/Cat' $ref: '#/components/schemas/Dog' $ref: '#/components/schemas/Lizard' ``` which means the payload MUST, by validation, match exactly one of the schemas described by `Cat`, `Dog`, or `Lizard`. In this case, a discriminator MAY act as a "hint" to shortcut validation and selection of the matching schema which may be a costly operation, depending on the complexity of the schema. We can then describe exactly which field tells us which schema to use: ```yaml MyResponseType: oneOf: $ref: '#/components/schemas/Cat' $ref: '#/components/schemas/Dog' $ref: '#/components/schemas/Lizard' discriminator: propertyName: petType ``` The expectation now is that a property with name `petType` MUST be present in the response payload, and the value will correspond to the name of a schema defined in the OAS document. Thus the response payload: ```json { "id": 12345, "petType": "Cat" } ``` Will indicate that the `Cat` schema be used in conjunction with this payload. In scenarios where the value of the discriminator field does not match the schema name or implicit mapping is not possible, an optional `mapping` definition MAY be used: ```yaml MyResponseType: oneOf: $ref: '#/components/schemas/Cat' $ref: '#/components/schemas/Dog' $ref: '#/components/schemas/Lizard' $ref: 'https://gigantic-server.com/schemas/Monster/schema.json' discriminator: propertyName: petType mapping: dog: '#/components/schemas/Dog' monster: 'https://gigantic-server.com/schemas/Monster/schema.json' ``` Here the discriminator value of `dog` will map to the schema `#/components/schemas/Dog`, rather than the default (implicit) value of `Dog`. If the discriminator value does not match an implicit or explicit mapping, no schema can be determined and validation SHOULD fail. Mapping keys MUST be string values, but tooling MAY convert response values to strings for comparison. When used in conjunction with the `anyOf` construct, the use of the discriminator can avoid ambiguity where multiple schemas may satisfy a single payload. In both the `oneOf` and `anyOf` use cases, all possible schemas MUST be listed explicitly. To avoid redundancy, the discriminator MAY be added to a parent schema definition, and all schemas comprising the parent schema in an `allOf` construct may be used as an alternate schema. For example: ```yaml components: schemas: Pet: type: object required: petType properties: petType: type: string discriminator: propertyName: petType mapping: dog: Dog Cat: allOf: $ref: '#/components/schemas/Pet' type: object properties: name: type: string Dog: allOf: $ref: '#/components/schemas/Pet' type: object properties: bark: type: string Lizard: allOf: $ref: '#/components/schemas/Pet' type: object properties: lovesRocks: type: boolean ``` a payload like this: ```json { "petType": "Cat", "name": "misty" } ``` will indicate that the `Cat` schema be used. Likewise this schema: ```json { "petType": "dog", "bark": "soft" } ``` will map to `Dog` because of the definition in the `mappings` element. A metadata object that allows for more fine-tuned XML model definitions. When using arrays, XML element names are not inferred (for singular/plural forms) and the `name` property SHOULD be used to add that information. See examples for expected behavior. Field Name | Type | Description |::| <a name="xmlName"></a>name | `string` | Replaces the name of the element/attribute used for the described schema property. When defined within `items`, it will affect the name of the individual XML elements within the list. When defined alongside `type` being `array` (outside the `items`), it will affect the wrapping element and only if `wrapped` is `true`. If `wrapped` is `false`, it will be ignored. <a name="xmlNamespace"></a>namespace | `string` | The URI of the namespace definition. Value MUST be in the form of an absolute URI. <a name="xmlPrefix"></a>prefix | `string` | The prefix to be used for the

<a name="xmlAttribute"></a>attribute | `boolean` | Declares whether the property definition translates to an attribute instead of an element. Default value is `false`. <a name="xmlWrapped"></a>wrapped | `boolean` | MAY be used only for an array definition. Signifies whether the array is wrapped (for example, `<books><book/><book/></books>`) or unwrapped (`<book/><book/>`). Default value is `false`. The definition takes effect only when defined alongside `type` being `array` (outside the `items`). This object MAY be extended with . The examples of the XML object definitions are included inside a property definition of a with a sample of the XML representation of it. Basic string property: ```json { "animals": { "type": "string" } } ``` ```yaml animals: type: string ``` ```xml <animals>...</animals> ``` Basic string array property ( is `false` by default): ```json { "animals": { "type": "array", "items": { "type": "string" } } } ``` ```yaml animals: type: array items: type: string ``` ```xml <animals>...</animals> <animals>...</animals> <animals>...</animals> ``` ```json { "animals": { "type": "string", "xml": { "name": "animal" } } } ``` ```yaml animals: type: string xml: name: animal ``` ```xml <animal>...</animal> ``` In this example, a full model definition is shown. ```json { "Person": { "type": "object", "properties": { "id": { "type": "integer", "format": "int32", "xml": { "attribute": true } }, "name": { "type": "string", "xml": { "namespace": "http://example.com/schema/sample", "prefix": "sample" } } } } } ``` ```yaml Person: type: object properties: id: type: integer format: int32 xml: attribute: true name: type: string xml: namespace: http://example.com/schema/sample prefix: sample ``` ```xml <Person id="123"> <sample:name xmlns:sample="http://example.com/schema/sample">example</sample:name> </Person> ``` Changing the element names: ```json { "animals": { "type": "array", "items": { "type": "string", "xml": { "name": "animal" } } } } ``` ```yaml animals: type: array items: type: string xml: name: animal ``` ```xml <animal>value</animal> <animal>value</animal> ``` The external `name` property has no effect on the XML: ```json { "animals": { "type": "array", "items": { "type": "string", "xml": { "name": "animal" } }, "xml": { "name": "aliens" } } } ``` ```yaml animals: type: array items: type: string xml: name: animal xml: name: aliens ``` ```xml <animal>value</animal> <animal>value</animal> ``` Even when the array is wrapped, if a name is not explicitly defined, the same name will be used both internally and externally: ```json { "animals": { "type": "array", "items": { "type": "string" }, "xml": { "wrapped": true } } } ``` ```yaml animals: type: array items: type: string xml: wrapped: true ``` ```xml <animals> <animals>value</animals> <animals>value</animals> </animals> ``` To overcome the naming problem in the example above, the following definition can be used: ```json { "animals": { "type": "array", "items": { "type": "string", "xml": { "name": "animal" } }, "xml": { "wrapped": true } } } ``` ```yaml animals: type: array items: type: string xml: name: animal xml: wrapped: true ``` ```xml <animals> <animal>value</animal> <animal>value</animal> </animals> ``` Affecting both internal and external names: ```json { "animals": { "type": "array", "items": { "type": "string", "xml": { "name": "animal" } }, "xml": { "name": "aliens", "wrapped": true } } } ``` ```yaml animals: type: array items: type: string xml: name: animal xml: name: aliens wrapped: true ``` ```xml <aliens> <animal>value</animal> <animal>value</animal> </aliens> ``` If we change the external element but not the internal ones: ```json { "animals": { "type": "array", "items": { "type": "string" }, "xml": { "name": "aliens", "wrapped": true } } } ``` ```yaml animals: type: array items: type: string xml: name: aliens wrapped: true ``` ```xml <aliens> <aliens>value</aliens> <aliens>value</aliens> </aliens> ``` Defines a security scheme that can be used by the

Supported schemes are HTTP authentication, an API key (either as a header, a cookie parameter or as a query parameter), OAuth2's common flows (implicit, password, application and access code) as defined in , and . Field Name | Type | Applies To | Description |::|| <a name="securitySchemeType"></a>type | `string` | Any | REQUIRED. The type of the security scheme. Valid values are `"apiKey"`, `"http"`, `"oauth2"`, `"openIdConnect"`. <a name="securitySchemeDescription"></a>description | `string` | Any | A short description for security scheme. MAY be used for rich text representation. <a name="securitySchemeName"></a>name | `string` | `apiKey` | REQUIRED. The name of the header, query or cookie parameter to be used. <a name="securitySchemeIn"></a>in | `string` | `apiKey` | REQUIRED. The location of the API key. Valid values are `"query"`, `"header"` or `"cookie"`. <a name="securitySchemeScheme"></a>scheme | `string` | `http` | REQUIRED. The name of the HTTP Authorization scheme to be used in the . <a name="securitySchemeBearerFormat"></a>bearerFormat | `string` | `http` (`"bearer"`) | A hint to the client to identify how the bearer token is formatted. Bearer tokens are usually generated by an authorization server, so this information is primarily for documentation purposes. <a name="securitySchemeFlows"></a>flows | | `oauth2` | REQUIRED. An object containing configuration information for the flow types supported. <a name="securitySchemeOpenIdConnectUrl"></a>openIdConnectUrl | `string` | `openIdConnect` | REQUIRED. OpenId Connect URL to discover OAuth2 configuration values. This MUST be in the form of a URL. This object MAY be extended with . ```json { "type": "http", "scheme": "basic" } ``` ```yaml type: http scheme: basic ``` ```json { "type": "apiKey", "name": "api_key", "in": "header" } ``` ```yaml type: apiKey name: api_key in: header ``` ```json { "type": "http", "scheme": "bearer", "bearerFormat": "JWT", } ``` ```yaml type: http scheme: bearer bearerFormat: JWT ``` ```json { "type": "oauth2", "flows": { "implicit": { "authorizationUrl": "https://example.com/api/oauth/dialog", "scopes": { "write:pets": "modify pets in your account", "read:pets": "read your pets" } } } } ``` ```yaml type: oauth2 flows: implicit: authorizationUrl: https://example.com/api/oauth/dialog scopes: write:pets: modify pets in your account read:pets: read your pets ``` Allows configuration of the supported OAuth Flows. Field Name | Type | Description |::| <a name="oauthFlowsImplicit"></a>implicit| | Configuration for the OAuth Implicit flow <a name="oauthFlowsPassword"></a>password| | Configuration for the OAuth Resource Owner Password flow <a name="oauthFlowsClientCredentials"></a>clientCredentials| | Configuration for the OAuth Client Credentials flow. Previously called `application` in OpenAPI 2.0. <a name="oauthFlowsAuthorizationCode"></a>authorizationCode| | Configuration for the OAuth Authorization Code flow. Previously called `accessCode` in OpenAPI 2.0. This object MAY be extended with . Configuration details for a supported OAuth Flow Field Name | Type | Applies To | Description |::|| <a name="oauthFlowAuthorizationUrl"></a>authorizationUrl | `string` | `oauth2` (`"implicit"`, `"authorizationCode"`) | REQUIRED. The authorization URL to be used for this flow. This MUST be in the form of a URL. <a name="oauthFlowTokenUrl"></a>tokenUrl | `string` | `oauth2` (`"password"`, `"clientCredentials"`, `"authorizationCode"`) | REQUIRED. The token URL to be used for this flow. This MUST be in the form of a URL. <a name="oauthFlowRefreshUrl"></a>refreshUrl | `string` | `oauth2` | The URL to be used for obtaining refresh tokens. This MUST be in the form of a URL. <a name="oauthFlowScopes"></a>scopes | Map[`string`, `string`] | `oauth2` | REQUIRED. The available scopes for the OAuth2 security scheme. A map between the scope name and a short description for it. This object MAY be extended with . ```JSON { "type": "oauth2", "flows": { "implicit": { "authorizationUrl": "https://example.com/api/oauth/dialog", "scopes": { "write:pets": "modify pets in your account", "read:pets": "read your pets" } }, "authorizationCode": { "authorizationUrl": "https://example.com/api/oauth/dialog", "tokenUrl": "https://example.com/api/oauth/token", "scopes": { "write:pets": "modify pets in your account", "read:pets": "read your pets" } } } } ``` ```yaml type: oauth2 flows: implicit: authorizationUrl:

scopes: write:pets: modify pets in your account read:pets: read your pets authorizationCode: authorizationUrl: https://example.com/api/oauth/dialog tokenUrl: https://example.com/api/oauth/token scopes: write:pets: modify pets in your account read:pets: read your pets ``` Lists the required security schemes to execute this operation. The name used for each property MUST correspond to a security scheme declared in the under the . Security Requirement Objects that contain multiple schemes require that all schemes MUST be satisfied for a request to be authorized. This enables support for scenarios where multiple query parameters or HTTP headers are required to convey security information. When a list of Security Requirement Objects is defined on the or , only one of the Security Requirement Objects in the list needs to be satisfied to authorize the request. Field Pattern | Type | Description |::| <a name="securityRequirementsName"></a>{name} | under the . If the security scheme is of type `"oauth2"` or `"openIdConnect"`, then the value is a list of scope names required for the execution. For other security scheme types, the array MUST be empty. ```json { "api_key": [] } ``` ```yaml api_key: [] ``` ```json { "petstore_auth": [ "write:pets", "read:pets" ] } ``` ```yaml petstore_auth: write:pets read:pets ``` While the OpenAPI Specification tries to accommodate most use cases, additional data can be added to extend the specification at certain points. The extensions properties are implemented as patterned fields that are always prefixed by `"x-"`. Field Pattern | Type | Description |::| <a name="infoExtensions"></a>^x- | Any | Allows extensions to the OpenAPI Schema. The field name MUST begin with `x-`, for example, `x-internal-id`. The value can be `null`, a primitive, an array or an object. Can have any valid JSON format value. The extensions may or may not be supported by the available tooling, but those may be extended as well to add requested support (if tools are internal or open-sourced). Some objects in the OpenAPI Specification MAY be declared and remain empty, or be completely removed, even though they are inherently the core of the API documentation. The reasoning is to allow an additional layer of access control over the documentation. While not part of the specification itself, certain libraries MAY choose to allow access to parts of the documentation based on some form of authentication/authorization. Two examples of this: The MAY be empty. It may be counterintuitive, but this may tell the viewer that they got to the right place, but can't access any documentation. They'd still have access to the which may contain additional information regarding authentication. The MAY be empty. In this case, the viewer will be aware that the path exists, but will not be able to see any of its operations or parameters. This is different than hiding the path itself from the , so the user will not be aware of its existence. This allows the documentation provider to finely control what the viewer can see. Version | Date | Notes | | 3.0.2 | 2018-10-08 | Patch release of the OpenAPI Specification 3.0.2 3.0.1 | 2017-12-06 | Patch release of the OpenAPI Specification 3.0.1 3.0.0 | 2017-07-26 | Release of the OpenAPI Specification 3.0.0 3.0.0-rc2 | 2017-06-16 | rc2 of the 3.0 specification 3.0.0-rc1 | 2017-04-27 | rc1 of the 3.0 specification 3.0.0-rc0 | 2017-02-28 | Implementer's Draft of the 3.0 specification 2.0 | 2015-12-31 | Donation of Swagger 2.0 to the Open API Initiative 2.0 | 2014-09-08 | Release of Swagger 2.0 1.2 | 2014-03-14 | Initial release of the formal document. 1.1 | 2012-08-22 | Release of Swagger 1.1 1.0 | 2011-08-10 | First release of the Swagger Specification