mcp-a2a-bridge

MCP-A2A Bridge

A lightweight Model Context Protocol (MCP) server that proxies requests to one or more remote A2A agents.

It lets tools that natively speak MCP – such as Claude, Cursor AI, or any other MCP-aware client – interact with agents that expose the A2A protocol.
In short: MCP on the front-end, A2A on the back-end.

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Why would I want this?

• Use your existing AI client as an A2A Client Use Claude Desktop, Cursor, etc. as a client that can connect to and use A2A servers

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MCP config in Claude / Cursor

To integrate with an MCP client that supports local servers (like Claude Desktop or Cursor), configure it to run the bridge using npx.

Example claude_desktop_config.json:

{
  "mcpServers": {
    "MCP-A2A Bridge": {
      "command": "npx",
      "args": [
        "-y", 
        "@agentopolis/mcp-a2a-bridge@latest", 
        "--a2a-server-config-dir=/Users/ryan/.config/mcp-a2a-bridge/servers" // Replace with your desired absolute path
      ]
    }
  }
}

Important:

• Replace /Users/ryan/.config/mcp-a2a-bridge/servers with the actual absolute path you want to use on your system.

Restart or refresh your application after adding this configuration. The bridge should appear as a new tool provider.

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Usage

Example: Send these prompts to your AI client:

1. Add an A2A server using its url

add this a2a server: https://a2a-demos.agentopolis.ai/bella-restaurant

2. Ask what skills the A2A server has:

what skills does Bella have?

3. Use the skills

What kind of specials are they running?

and

Make a reservation for two for thursday at 8pm, under the name Ryan

Screenshots using Claude Desktop

1. Adding an A2A server

2. Checking the MCP Tools

4. Asking about specials

5. Making a reservation

6. Listing servers

Configuration Directory

The bridge stores A2A server registrations as JSON files. The location is determined as follows:

1. --a2a-server-config-dir=/your/absolute/path (CLI flag - Recommended)
2. ./.mcp-a2a-servers (Relative to the current working directory of the bridge process – default if the CLI flag is not set. This may be unpredictable when run by other tools.)

A typical entry lives at <config_dir>/<serverId>.json.

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Available MCP tools

Tool name	Purpose	Input schema
a2a_register_server	Fetches an A2A agent's card from <url>/.well-known/agent.json and saves it.	{ url: string }
a2a_reload_servers	Re-reads all JSON files in the config directory.	none
a2a_list_servers	Lists registered servers.	none
a2a_get_server_details	Full card for a given server.	{ serverId: string }
a2a_remove_server	Delete a registration.	{ serverId: string }
a2a_send_task	Generic escape hatch – call any A2A agent with an arbitrary message.	`{ serverId: string; taskId: string; message?: string
<serverId>_<skillId>	Auto-generated. One tool per skill on every registered agent. Accepts { message: string }.	—

A <serverId>_<skillId> tool name is slugified (my-agent + provide-restaurant-info → my-agent_provide-restaurant-info).

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Released under the MIT license.