OpenAI APIs Messages API

openapi: 3.1.0
info:
  title: OpenAI APIs OpenAI Assistants Messages API
  description: API for building AI assistants with custom instructions, knowledge retrieval, code execution, and function calling capabilities. Supports managing assistants, threads, messages, and runs.
  version: '2.0'
  contact:
    name: OpenAI Support
    email: support@openai.com
    url: https://help.openai.com
  termsOfService: https://openai.com/policies/terms-of-use
servers:
- url: https://api.openai.com/v1
  description: OpenAI Production API
security:
- bearerAuth: []
tags:
- name: Messages
  description: Manage messages within threads
paths:
  /threads/{thread_id}/messages:
    get:
      operationId: listMessages
      summary: OpenAI APIs List messages
      description: Returns a list of messages for a given thread.
      tags:
      - Messages
      parameters:
      - $ref: '#/components/parameters/threadId'
      - $ref: '#/components/parameters/limit'
      - $ref: '#/components/parameters/order'
      - $ref: '#/components/parameters/after'
      - $ref: '#/components/parameters/before'
      - $ref: '#/components/parameters/OpenAIBeta'
      responses:
        '200':
          description: List of messages
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ListResponse'
    post:
      operationId: createMessage
      summary: OpenAI APIs Create message
      description: Create a message within a thread.
      tags:
      - Messages
      parameters:
      - $ref: '#/components/parameters/threadId'
      - $ref: '#/components/parameters/OpenAIBeta'
      requestBody:
        required: true
        content:
          application/json:
            schema:
              $ref: '#/components/schemas/CreateMessageRequest'
      responses:
        '200':
          description: Message created
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Message'
        '400':
          description: Invalid request
  /threads/{thread_id}/messages/{message_id}:
    get:
      operationId: getMessage
      summary: OpenAI APIs Retrieve message
      description: Retrieve a message by ID.
      tags:
      - Messages
      parameters:
      - $ref: '#/components/parameters/threadId'
      - $ref: '#/components/parameters/messageId'
      - $ref: '#/components/parameters/OpenAIBeta'
      responses:
        '200':
          description: Message details
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Message'
        '404':
          description: Message not found
components:
  parameters:
    order:
      name: order
      in: query
      description: Sort order by created_at timestamp
      schema:
        type: string
        enum:
        - asc
        - desc
        default: desc
    after:
      name: after
      in: query
      description: A cursor for pagination (object ID to start after)
      schema:
        type: string
    threadId:
      name: thread_id
      in: path
      required: true
      description: The ID of the thread
      schema:
        type: string
    messageId:
      name: message_id
      in: path
      required: true
      description: The ID of the message
      schema:
        type: string
    before:
      name: before
      in: query
      description: A cursor for pagination (object ID to end before)
      schema:
        type: string
    OpenAIBeta:
      name: OpenAI-Beta
      in: header
      required: true
      description: Required header for the Assistants API beta
      schema:
        type: string
        enum:
        - assistants=v2
    limit:
      name: limit
      in: query
      description: Maximum number of objects to return (1-100, default 20)
      schema:
        type: integer
        minimum: 1
        maximum: 100
        default: 20
  schemas:
    ListResponse:
      type: object
      properties:
        object:
          type: string
          enum:
          - list
        data:
          type: array
          items:
            type: object
        first_id:
          type: string
        last_id:
          type: string
        has_more:
          type: boolean
    CreateMessageRequest:
      type: object
      required:
      - role
      - content
      properties:
        role:
          type: string
          enum:
          - user
          - assistant
          description: The role of the entity creating the message
        content:
          oneOf:
          - type: string
          - type: array
            items:
              type: object
          description: The content of the message
        metadata:
          type: object
          description: Key-value metadata for the message
    Message:
      type: object
      properties:
        id:
          type: string
          description: The identifier of the message
        object:
          type: string
          enum:
          - thread.message
        created_at:
          type: integer
          description: Unix timestamp of creation
        thread_id:
          type: string
          description: The thread this message belongs to
        role:
          type: string
          enum:
          - user
          - assistant
          description: The role of the entity that produced the message
        content:
          type: array
          items:
            type: object
            properties:
              type:
                type: string
                enum:
                - text
                - image_file
                - image_url
              text:
                type: object
                properties:
                  value:
                    type: string
                  annotations:
                    type: array
                    items:
                      type: object
          description: The content of the message
        assistant_id:
          type: string
          nullable: true
          description: The assistant that authored this message
        run_id:
          type: string
          nullable: true
          description: The run associated with this message
        metadata:
          type: object
          description: Key-value metadata attached to the message
  securitySchemes:
    bearerAuth:
      type: http
      scheme: bearer
      bearerFormat: API Key
      description: OpenAI API key passed as a Bearer token
externalDocs:
  description: OpenAI Assistants API Documentation
  url: https://platform.openai.com/docs/api-reference/assistants