> ## Documentation Index
> Fetch the complete documentation index at: https://langchain-5e9cc07a-preview-devupd-1765394015-eccef47.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# A2A Post

> Communicate with an assistant using the Agent-to-Agent Protocol.
Sends a JSON-RPC 2.0 message to the assistant.

- **Request**: Provide an object with `jsonrpc`, `id`, `method`, and optional `params`.
- **Response**: Returns a JSON-RPC response with task information or error.

**Supported Methods:**
- `message/send`: Send a message to the assistant
- `tasks/get`: Get the status and result of a task

**Notes:**
- Supports threaded conversations via thread context
- Messages can contain text and data parts
- Tasks run asynchronously and return completion status




## OpenAPI

````yaml langsmith/agent-server-openapi.json post /a2a/{assistant_id}
openapi: 3.1.0
info:
  title: LangSmith Deployment
  version: 0.1.0
servers: []
security: []
tags:
  - name: Assistants
    description: An assistant is a configured instance of a graph.
  - name: Threads
    description: A thread contains the accumulated outputs of a group of runs.
  - name: Thread Runs
    description: >-
      A run is an invocation of a graph / assistant on a thread. It updates the
      state of the thread.
  - name: Stateless Runs
    description: >-
      A run is an invocation of a graph / assistant, with no state or memory
      persistence.
  - name: Crons (Plus tier)
    description: >-
      A cron is a periodic run that recurs on a given schedule. The repeats can
      be isolated, or share state in a thread
  - name: Store
    description: >-
      Store is an API for managing persistent key-value store (long-term memory)
      that is available from any thread.
  - name: A2A
    description: >-
      Agent-to-Agent Protocol related endpoints for exposing assistants as
      A2A-compliant agents.
  - name: MCP
    description: >-
      Model Context Protocol related endpoints for exposing an agent as an MCP
      server.
  - name: System
    description: System endpoints for health checks, metrics, and server information.
paths:
  /a2a/{assistant_id}:
    post:
      tags:
        - A2A
      summary: A2A Post
      description: >
        Communicate with an assistant using the Agent-to-Agent Protocol.

        Sends a JSON-RPC 2.0 message to the assistant.


        - **Request**: Provide an object with `jsonrpc`, `id`, `method`, and
        optional `params`.

        - **Response**: Returns a JSON-RPC response with task information or
        error.


        **Supported Methods:**

        - `message/send`: Send a message to the assistant

        - `tasks/get`: Get the status and result of a task


        **Notes:**

        - Supports threaded conversations via thread context

        - Messages can contain text and data parts

        - Tasks run asynchronously and return completion status
      operationId: post_a2a
      parameters:
        - name: assistant_id
          in: path
          required: true
          schema:
            type: string
            format: uuid
          description: The ID of the assistant to communicate with
        - name: Accept
          in: header
          required: true
          schema:
            type: string
            enum:
              - application/json
          description: Must be application/json
      requestBody:
        required: true
        content:
          application/json:
            schema:
              type: object
              properties:
                jsonrpc:
                  type: string
                  enum:
                    - '2.0'
                  description: JSON-RPC version
                id:
                  type: string
                  description: Request identifier
                method:
                  type: string
                  enum:
                    - message/send
                    - tasks/get
                  description: The method to invoke
                params:
                  type: object
                  description: Method parameters
                  oneOf:
                    - title: Message Send Parameters
                      properties:
                        message:
                          type: object
                          properties:
                            role:
                              type: string
                              enum:
                                - user
                                - assistant
                              description: Message role
                            parts:
                              type: array
                              items:
                                oneOf:
                                  - title: Text Part
                                    type: object
                                    properties:
                                      kind:
                                        type: string
                                        enum:
                                          - text
                                      text:
                                        type: string
                                    required:
                                      - kind
                                      - text
                                  - title: Data Part
                                    type: object
                                    properties:
                                      kind:
                                        type: string
                                        enum:
                                          - data
                                      data:
                                        type: object
                                    required:
                                      - kind
                                      - data
                              description: Message parts
                            messageId:
                              type: string
                              description: Unique message identifier
                          required:
                            - role
                            - parts
                            - messageId
                        thread:
                          type: object
                          properties:
                            threadId:
                              type: string
                              description: Thread identifier for conversation context
                          description: Optional thread context
                      required:
                        - message
                    - title: Task Get Parameters
                      properties:
                        taskId:
                          type: string
                          description: Task identifier to retrieve
                      required:
                        - taskId
              required:
                - jsonrpc
                - id
                - method
      responses:
        '200':
          description: JSON-RPC response
          content:
            application/json:
              schema:
                type: object
                properties:
                  jsonrpc:
                    type: string
                    enum:
                      - '2.0'
                  id:
                    type: string
                  result:
                    type: object
                    description: Success result containing task information or task details
                  error:
                    type: object
                    properties:
                      code:
                        type: integer
                      message:
                        type: string
                    description: Error information if request failed
                required:
                  - jsonrpc
                  - id
        '400':
          description: Bad request - invalid JSON-RPC or missing Accept header
        '404':
          description: Assistant not found
        '500':
          description: Internal server error

````