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.add_default_value', 'description': 'Adds a default value to a dictionary if the specified key does not exist, ensuring that updates do not overwrite existing entries. Note that the provided function is in Python 3 syntax.', 'parameters': {'type': 'dict', 'required': ['dict', 'key', 'default_value'], 'properties': {'dict': {'type': 'dict', 'description': 'The dictionary to which the default value should be added.', 'properties': {}}, 'key': {'type': 'string', 'description': 'The key for which the default value is to be set.'}, 'default_value': {'type': 'any', 'description': 'The value to set for the key if it does not exist in the dictionary. The type of this value can be any valid Python data type.'}}}}, {'name': 'add_mtnards_server', 'description': 'Adds a new MTNA (Mobile Telecommunications Network Architecture) Rich Data Services (RDS) server to the environment, allowing for the management and retrieval of rich data. Note that the provided function is in Python 3 syntax.', 'parameters': {'type': 'dict', 'required': ['api_key'], 'properties': {'nickname': {'type': 'string', 'description': "A user-friendly name to identify the server. For example, 'primary_db_server'.", 'default': 'local_rds_server'}, 'host': {'type': 'string', 'description': "The hostname or IP address of the RDS server. Defaults to 'localhost' if not specified.", 'default': 'localhost'}, 'api_key': {'type': 'string', 'description': 'A unique API key for authenticating requests to the RDS server. This key should be kept secret.'}}}}, {'name': 'add_postgres_server', 'description': 'Add a new PostgreSQL server configuration to the environment allowing the application to connect to it. 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 to identify the PostgreSQL server.'}, 'host': {'type': 'string', 'description': 'The network address or domain of the PostgreSQL server.'}, 'port': {'type': 'integer', 'description': 'The network port that the PostgreSQL server is listening on.'}, 'database': {'type': 'string', 'description': 'The name of the default database to connect to.'}, 'username': {'type': 'string', 'description': 'The username used to authenticate with the PostgreSQL server.'}, 'password': {'type': 'string', 'description': 'The password used to authenticate with the PostgreSQL server. Must be provided for security reasons.'}}}}, {'name': 'dartfx_help', 'description': 'Provides a help guide or assistance information for using the DartFX application. Note that the provided function is in Python 3 syntax.', 'parameters': {'type': 'dict', 'required': ['topic'], 'properties': {'topic': {'type': 'string', 'description': "The topic for which help is requested, such as 'installation', 'configuration', 'usage'.", 'enum': ['installation', 'configuration', 'usage', 'troubleshooting']}, 'language': {'type': 'string', 'description': 'The language in which the help content is to be provided. Defaults to English.', 'enum': ['English', 'Spanish', 'French', 'German'], 'default': 'English'}, 'include_examples': {'type': 'boolean', 'description': 'Flag to indicate if practical examples should be included in the help content.', 'default': True}}}}, {'name': 'list_servers', 'description': 'Retrieves a list of servers from the specified environment, filtered by the server type if provided. Note that the provided function is in Python 3 syntax.', 'parameters': {'type': 'dict', 'required': [], 'properties': {'type': {'type': 'string', 'description': 'Specifies the type of server to filter the list. If omitted, servers of all types are listed.', 'enum': ['all', 'postgres', 'openapi', 'graphql'], 'default': 'all'}}}}]


user: List all PostgreSQL servers from our environment?

Available functions:
[{"name": "default.add_default_value", "description": "Adds a default value to a dictionary if the specified key does not exist, ensuring that updates do not overwrite existing entries.", "parameters": {"type": "dict", "required": ["dict", "key", "default_value"], "properties": {"dict": {"type": "dict", "description": "The dictionary to which the default value should be added.", "properties": {}}, "key": {"type": "string", "description": "The key for which the default value is to be set."}, "default_value": {"type": "any", "description": "The value to set for the key if it does not exist in the dictionary. The type of this value can be any valid Python data type."}}}}, {"name": "add_mtnards_server", "description": "Adds a new MTNA (Mobile Telecommunications Network Architecture) Rich Data Services (RDS) server to the environment, allowing for the management and retrieval of rich data.", "parameters": {"type": "dict", "required": ["api_key"], "properties": {"nickname": {"type": "string", "description": "A user-friendly name to identify the server. For example, 'primary_db_server'.", "default": "local_rds_server"}, "host": {"type": "string", "description": "The hostname or IP address of the RDS server. Defaults to 'localhost' if not specified.", "default": "localhost"}, "api_key": {"type": "string", "description": "A unique API key for authenticating requests to the RDS server. This key should be kept secret."}}}}, {"name": "add_postgres_server", "description": "Add a new PostgreSQL server configuration to the environment allowing the application to connect to it.", "parameters": {"type": "dict", "required": ["nickname", "host", "port", "database", "username", "password"], "properties": {"nickname": {"type": "string", "description": "A unique and recognizable name to identify the PostgreSQL server."}, "host": {"type": "string", "description": "The network address or domain of the PostgreSQL server."}, "port": {"type": "integer", "description": "The network port that the PostgreSQL server is listening on."}, "database": {"type": "string", "description": "The name of the default database to connect to."}, "username": {"type": "string", "description": "The username used to authenticate with the PostgreSQL server."}, "password": {"type": "string", "description": "The password used to authenticate with the PostgreSQL server. Must be provided for security reasons."}}}}, {"name": "dartfx_help", "description": "Provides a help guide or assistance information for using the DartFX application.", "parameters": {"type": "dict", "required": ["topic"], "properties": {"topic": {"type": "string", "description": "The topic for which help is requested, such as 'installation', 'configuration', 'usage'.", "enum": ["installation", "configuration", "usage", "troubleshooting"]}, "language": {"type": "string", "description": "The language in which the help content is to be provided. Defaults to English.", "enum": ["English", "Spanish", "French", "German"], "default": "English"}, "include_examples": {"type": "boolean", "description": "Flag to indicate if practical examples should be included in the help content.", "default": true}}}}, {"name": "list_servers", "description": "Retrieves a list of servers from the specified environment, filtered by the server type if provided.", "parameters": {"type": "dict", "required": [], "properties": {"type": {"type": "string", "description": "Specifies the type of server to filter the list. If omitted, servers of all types are listed.", "enum": ["all", "postgres", "openapi", "graphql"], "default": "all"}}}}]

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