system: 
You are an expert in composing functions. You are given a question and a set of possible functions.
Based on the question, you will need to make one or more function/tool calls to achieve the purpose.
If none of the function can be used, point it out. If the given question lacks the parameters required by the function,
also point it out. You should only return the function call in tools call sections.

If you decide to invoke any of the function(s), you MUST put it in the format of [func_name1(params_name1=params_value1, params_name2=params_value2...), func_name2(params)]

You SHOULD NOT include any other text in the response.

Here is a list of functions in JSON format that you can invoke.

[{'name': 'default_function', 'description': 'This function provides default behavior when specific functionality has not been implemented. Note that the provided function is in Python 3 syntax.', 'parameters': {'type': 'dict', 'required': ['action'], 'properties': {'action': {'type': 'string', 'description': 'The action to be executed by the function. Should be a descriptive verb.', 'enum': ['create', 'read', 'update', 'delete']}, 'verbose': {'type': 'boolean', 'description': 'A flag to indicate whether to run the function in verbose mode, providing detailed logs.', 'default': False}, 'timeout': {'type': 'integer', 'description': 'Maximum time in seconds the function should wait before timing out.', 'default': 60}}}}, {'name': 'add_mtnards_server', 'description': 'Adds a new MTNA Rich Data Services (RDS) server to the environment configuration, allowing it to be recognized and utilized by the system. Note that the provided function is in Python 3 syntax.', 'parameters': {'type': 'dict', 'required': ['host', 'api_key'], 'properties': {'nickname': {'type': 'string', 'description': 'An informal, easy-to-remember name for the server.', 'default': 'rds1'}, 'host': {'type': 'string', 'description': "The server's hostname or IP address. Should be in the format 'hostname.com' or '192.168.0.1'."}, 'api_key': {'type': 'string', 'description': 'A unique API key for secure access to the server.'}}}}, {'name': 'add_postgres_server', 'description': 'Adds a new PostgreSQL server configuration to the environment, allowing for future database operations on this server. Note that the provided function is in Python 3 syntax.', 'parameters': {'type': 'dict', 'required': ['nickname', 'host', 'port', 'database', 'username', 'password'], 'properties': {'nickname': {'type': 'string', 'description': 'A unique and recognizable name or alias for the server, used for easy identification.'}, 'host': {'type': 'string', 'description': 'The hostname or IP address of the PostgreSQL server.'}, 'port': {'type': 'integer', 'description': 'The network port on which the PostgreSQL server is listening.'}, 'database': {'type': 'string', 'description': 'The default database name to connect to on the PostgreSQL server.'}, 'username': {'type': 'string', 'description': 'The username for authentication with the PostgreSQL server.'}, 'password': {'type': 'string', 'description': 'The password associated with the username for authentication with the PostgreSQL server.'}}}}, {'name': 'dartfx_help', 'description': 'Provides guidance and assistance to the user on a particular topic within the DartFX application. Note that the provided function is in Python 3 syntax.', 'parameters': {'type': 'dict', 'required': ['topic'], 'properties': {'topic': {'type': 'string', 'description': "The specific topic or feature within DartFX the user needs help with, such as 'chart analysis' or 'trade execution'."}, 'verbose': {'type': 'boolean', 'description': 'Whether to provide detailed assistance. If true, the help provided will include comprehensive information and examples.', 'default': False}, 'language': {'type': 'string', 'description': 'The language in which the help is to be provided.', 'enum': ['English', 'Spanish', 'French', 'German', 'Chinese'], 'default': 'English'}}}}, {'name': 'list_servers', 'description': 'Retrieve a list of all servers within a specified environment, optionally filtered by server type. Note that the provided function is in Python 3 syntax.', 'parameters': {'type': 'dict', 'properties': {'server_type': {'type': 'string', 'description': 'The category of servers to list. If not specified, all server types are included.', 'enum': ['all', 'graphql', 'mtna', 'openapi', 'postgres', 'rds', 'sql'], 'default': 'all'}}, 'required': []}}]


user: Could you retrieve a list of all the PostgreSQL servers in our environment, please?

Available functions:
[{"name": "default_function", "description": "This function provides default behavior when specific functionality has not been implemented.", "parameters": {"type": "dict", "required": ["action"], "properties": {"action": {"type": "string", "description": "The action to be executed by the function. Should be a descriptive verb.", "enum": ["create", "read", "update", "delete"]}, "verbose": {"type": "boolean", "description": "A flag to indicate whether to run the function in verbose mode, providing detailed logs.", "default": false}, "timeout": {"type": "integer", "description": "Maximum time in seconds the function should wait before timing out.", "default": 60}}}}, {"name": "add_mtnards_server", "description": "Adds a new MTNA Rich Data Services (RDS) server to the environment configuration, allowing it to be recognized and utilized by the system.", "parameters": {"type": "dict", "required": ["host", "api_key"], "properties": {"nickname": {"type": "string", "description": "An informal, easy-to-remember name for the server.", "default": "rds1"}, "host": {"type": "string", "description": "The server's hostname or IP address. Should be in the format 'hostname.com' or '192.168.0.1'."}, "api_key": {"type": "string", "description": "A unique API key for secure access to the server."}}}}, {"name": "add_postgres_server", "description": "Adds a new PostgreSQL server configuration to the environment, allowing for future database operations on this server.", "parameters": {"type": "dict", "required": ["nickname", "host", "port", "database", "username", "password"], "properties": {"nickname": {"type": "string", "description": "A unique and recognizable name or alias for the server, used for easy identification."}, "host": {"type": "string", "description": "The hostname or IP address of the PostgreSQL server."}, "port": {"type": "integer", "description": "The network port on which the PostgreSQL server is listening."}, "database": {"type": "string", "description": "The default database name to connect to on the PostgreSQL server."}, "username": {"type": "string", "description": "The username for authentication with the PostgreSQL server."}, "password": {"type": "string", "description": "The password associated with the username for authentication with the PostgreSQL server."}}}}, {"name": "dartfx_help", "description": "Provides guidance and assistance to the user on a particular topic within the DartFX application.", "parameters": {"type": "dict", "required": ["topic"], "properties": {"topic": {"type": "string", "description": "The specific topic or feature within DartFX the user needs help with, such as 'chart analysis' or 'trade execution'."}, "verbose": {"type": "boolean", "description": "Whether to provide detailed assistance. If true, the help provided will include comprehensive information and examples.", "default": false}, "language": {"type": "string", "description": "The language in which the help is to be provided.", "enum": ["English", "Spanish", "French", "German", "Chinese"], "default": "English"}}}}, {"name": "list_servers", "description": "Retrieve a list of all servers within a specified environment, optionally filtered by server type.", "parameters": {"type": "dict", "properties": {"server_type": {"type": "string", "description": "The category of servers to list. If not specified, all server types are included.", "enum": ["all", "graphql", "mtna", "openapi", "postgres", "rds", "sql"], "default": "all"}}, "required": []}}]

Ground-truth function call:
[{"list_servers": {"server_type": ["postgres"]}}]