---
title: "Invoke Agent A2A"
method: POST
path: "/a2a/{agent_id}/message/send"
tags: ["a2a"]
---

# Invoke Agent A2A

`POST /a2a/{agent_id}/message/send`

Invoke an agent using the A2A protocol (JSON-RPC 2.0).

Supported methods:
- message/send: Send a message and get a response
- message/stream: Send a message and stream the response

## Path parameters

- `agent_id` string, required

## Response `200`

Successful Response

- unknown

## Other responses

- `422` — Validation Error

## Changes

- **2026-09-18** `082b5fabd909` — 2 info
  - added the optional property `detail/items/ctx` to the response with the `422` status
  - added the optional property `detail/items/input` to the response with the `422` status

[Change history](https://skmtc.dev/flock/apis/litellm-api/changes/a2a/:agent_id/message/send/post.md)

---

[API](https://skmtc.dev/flock/apis/litellm-api.md) · [All operations](https://skmtc.dev/flock/apis/litellm-api/llms.txt) · [OpenAPI document](https://skmtc.dev/flock/apis/litellm-api/revisions/3b2b241e4b0b?raw)