> ## Documentation Index > Fetch the complete documentation index at: https://docs.retellai.com/llms.txt > Use this file to discover all available pages before exploring further. # Create Chat Completion > Create a chat completion message ## OpenAPI ````yaml openapi-final post /create-chat-completion openapi: 3.0.3 info: title: Retell SDK version: 3.0.0 contact: name: Retell Support url: https://www.retellai.com/ email: support@retellai.com license: name: Apache 2.0 url: https://www.apache.org/licenses/LICENSE-2.0.html servers: - url: https://api.retellai.com description: The production server. security: - api_key: [] paths: /create-chat-completion: post: description: Create a chat completion message operationId: createChatCompletion requestBody: required: true content: application/json: schema: type: object required: - chat_id - content properties: chat_id: type: string example: oBeDLoLOeuAbiuaMFXRtDOLriTJ5tSxD description: Unique id of the chat to create completion. content: type: string example: hi how are you doing? description: user message to generate agent chat completion. responses: '201': description: Successfully created chat completion. content: application/json: schema: type: object required: - messages properties: messages: type: array items: $ref: '#/components/schemas/MessageOrToolCall' description: >- New messages generated by the agent during this completion, including any tool call invocations and their results. Does not include the original input messages. '400': $ref: '#/components/responses/BadRequest' '401': $ref: '#/components/responses/Unauthorized' '402': $ref: '#/components/responses/PaymentRequired' '422': $ref: '#/components/responses/UnprocessableContent' '429': $ref: '#/components/responses/TooManyRequests' '500': $ref: '#/components/responses/InternalServerError' x-codeSamples: - lang: JavaScript source: |- import Retell from 'retell-sdk'; const client = new Retell({ apiKey: process.env['RETELL_API_KEY'], // This is the default and can be omitted }); const response = await client.chat.createChatCompletion({ chat_id: 'oBeDLoLOeuAbiuaMFXRtDOLriTJ5tSxD', content: 'hi how are you doing?', }); console.log(response.messages); - lang: Python source: |- import os from retell import Retell client = Retell( api_key=os.environ.get("RETELL_API_KEY"), # This is the default and can be omitted ) response = client.chat.create_chat_completion( chat_id="oBeDLoLOeuAbiuaMFXRtDOLriTJ5tSxD", content="hi how are you doing?", ) print(response.messages) components: schemas: MessageOrToolCall: oneOf: - $ref: '#/components/schemas/Message' - $ref: '#/components/schemas/ToolCallInvocationMessage' - $ref: '#/components/schemas/ToolCallResultMessage' - $ref: '#/components/schemas/NodeTransitionMessage' - $ref: '#/components/schemas/StateTransitionMessage' Message: allOf: - $ref: '#/components/schemas/MessageBase' - required: - message_id - created_timestamp ToolCallInvocationMessage: allOf: - $ref: '#/components/schemas/ToolCallInvocationMessageBase' - required: - message_id - created_timestamp ToolCallResultMessage: allOf: - $ref: '#/components/schemas/ToolCallResultMessageBase' - required: - message_id - created_timestamp NodeTransitionMessage: allOf: - $ref: '#/components/schemas/NodeTransitionMessageBase' - required: - message_id - created_timestamp StateTransitionMessage: allOf: - $ref: '#/components/schemas/StateTransitionMessageBase' - required: - message_id - created_timestamp MessageBase: type: object required: - role - content properties: message_id: type: string example: Jabr9TXYYJHfvl6Syypi88rdAHYHmcq6 description: Unique id of the message role: type: string enum: - agent - user description: Documents whether this message is sent by agent or user. example: agent content: type: string description: Content of the message example: hi how are you doing? created_timestamp: type: integer description: Create timestamp of the message example: 1703302428855 ToolCallInvocationMessageBase: type: object required: - role - tool_call_id - name - arguments properties: message_id: type: string example: Jabr9TXYYJHfvl6Syypi88rdAHYHmcq6 description: Unique id of the message role: type: string enum: - tool_call_invocation description: This is a tool call invocation. tool_call_id: type: string description: Tool call id, globally unique. name: type: string description: Name of the function in this tool call. arguments: type: string description: Arguments for this tool call, it's a stringified JSON object. thought_signature: type: string description: >- Optional thought signature from Google Gemini thinking models. This is used internally to maintain reasoning chain in multi-turn function calling. created_timestamp: type: integer description: Create timestamp of the message example: 1703302428855 ToolCallResultMessageBase: type: object required: - role - tool_call_id - content properties: message_id: type: string example: Jabr9TXYYJHfvl6Syypi88rdAHYHmcq6 description: Unique id of the message role: type: string enum: - tool_call_result description: This is the result of a tool call. tool_call_id: type: string description: Tool call id, globally unique. content: type: string description: Result of the tool call, can be a string, a stringified json, etc. successful: type: boolean description: Whether the tool call was successful. created_timestamp: type: integer description: Create timestamp of the message example: 1703302428855 NodeTransitionMessageBase: type: object required: - role properties: message_id: type: string example: Jabr9TXYYJHfvl6Syypi88rdAHYHmcq6 description: Unique id of the message role: type: string enum: - node_transition description: This is a node transition. former_node_id: type: string description: Former node id former_node_name: type: string description: Former node name new_node_id: type: string description: New node id new_node_name: type: string description: New node name transition_type: type: string enum: - global - global_go_back - interrupt_go_back - normal description: >- How this node was reached. "global" means a global node transition, "global_go_back" means returning from a global node, "interrupt_go_back" means going back due to user interruption, and "normal" means a regular edge transition. created_timestamp: type: integer description: Create timestamp of the message example: 1703302428855 StateTransitionMessageBase: type: object required: - role properties: message_id: type: string example: Jabr9TXYYJHfvl6Syypi88rdAHYHmcq6 description: Unique id of the message role: type: string enum: - state_transition description: This is a state transition. former_state_name: type: string description: Former state name new_state_name: type: string description: New state name created_timestamp: type: integer description: Create timestamp of the message example: 1703302428855 responses: BadRequest: description: Bad Request content: application/json: schema: type: object properties: status: type: string enum: - error message: type: string example: Invalid request format, please check API reference. Unauthorized: description: Unauthorized content: application/json: schema: type: object properties: status: type: string enum: - error message: type: string example: API key is missing or invalid. PaymentRequired: description: Payment Required content: application/json: schema: type: object properties: status: type: string enum: - error message: type: string example: Trial has ended, please add payment method. UnprocessableContent: description: Unprocessable Content content: application/json: schema: type: object properties: status: type: string enum: - error message: type: string example: Cannot find requested asset under given api key. TooManyRequests: description: Too Many Requests content: application/json: schema: type: object properties: status: type: string enum: - error message: type: string example: Account rate limited, please throttle your requests. InternalServerError: description: Internal Server Error content: application/json: schema: type: object properties: status: type: string enum: - error message: type: string example: An unexpected server error occurred. securitySchemes: api_key: type: http scheme: bearer bearerFormat: string description: >- Authentication header containing API key (find it in dashboard). The format is "Bearer YOUR_API_KEY" ````