A2A Bridge for OpenClaw

Bridges the standard A2A protocol (Agent-to-Agent) to OpenClaw's internal chat completions endpoint. Enables bidirectional A2A communication between OpenClaw and external agents.

What it does

• Serves an agent card at /.well-known/agent-card.json so external A2A agents can discover your OpenClaw instance
• Handles inbound A2A requests at /a2a — external agents call OpenClaw via standard JSON-RPC message/send
• Provides tools for outbound calls — OpenClaw can call remote A2A agents using a2a_call_remote

External Agent                        OpenClaw (:18789)
├── a2a_call("krolik")   ──────→      ├── a2a-bridge plugin
│                                     │   ├── /.well-known/agent-card.json
│                                     │   ├── /a2a (JSON-RPC)
│                                     │   └── → /v1/chat/completions
│                        ←──────      │
├── A2A Server           ←──────      ├── a2a_call_remote tool

Prerequisites

• OpenClaw with the chat completions HTTP endpoint enabled:

  {
    "gateway": {
      "http": {
        "endpoints": {
          "chatCompletions": { "enabled": true }
        }
      }
    }
  }
  

Installation

Clone the plugin into your OpenClaw extensions directory:

cd ~/.openclaw/extensions
git clone https://github.com/anatolykoptev/openclaw-a2a-bridge a2a-bridge

Then register it in ~/.openclaw/openclaw.json:

{
  "plugins": {
    "allow": ["a2a-bridge"],
    "entries": {
      "a2a-bridge": {
        "enabled": true,
        "config": {
          "secret": "your-bearer-token-here",
          "remoteAgents": {
            "example-agent": {
              "url": "http://127.0.0.1:9000",
              "token": "remote-agent-token",
              "alias": "Example Agent"
            }
          }
        }
      }
    }
  }
}

Restart OpenClaw to load the plugin.

Configuration

Agent card customization

The agent card served at /.well-known/agent-card.json uses the agent name from OpenClaw config. The card advertises:

• Protocol version: 0.3.0
• Transport: JSON-RPC (non-streaming)
• Security: Bearer token (when secret is set)

Tools

The plugin registers three tools:

a2a_call_remote

Send a message to a remote A2A agent and get a response.

a2a_list_remote_agents

List all configured remote A2A agents. No parameters.

a2a_discover_remote

Fetch the agent card (capabilities, skills) of a remote A2A agent.

A2A Protocol Details

Inbound (external agent calls OpenClaw)

The plugin handles message/send JSON-RPC method:

{
  "jsonrpc": "2.0",
  "method": "message/send",
  "id": 1,
  "params": {
    "message": {
      "messageId": "uuid",
      "role": "user",
      "parts": [{ "kind": "text", "text": "Hello" }]
    }
  }
}

Response:

{
  "jsonrpc": "2.0",
  "id": 1,
  "result": {
    "id": "task-uuid",
    "contextId": "context-uuid",
    "status": { "state": "completed" },
    "artifacts": [
      { "parts": [{ "kind": "text", "text": "Response from OpenClaw" }] }
    ]
  }
}

Authentication

Inbound requests are authenticated via Authorization: Bearer <token> header (or X-Webhook-Secret for compatibility). The token is compared against the configured secret using constant-time comparison.

License

MIT