a2a-mcp-connector

A generic MCP server that stream-connects an AI agent to any standard A2A endpoint — plus a built-in A2A Agent Card validator. Install it once in your MCP-capable agent (Claude Code, Codex, Cursor, …) and you can validate and drive any A2A agent over the standard input-required multi-turn protocol, with no manual a2a-sdk install and no per-endpoint code.

It is deliberately provider-agnostic: there is no LLM and no API key inside this server. It is a pure standard-A2A client bridge — your agent is the intelligence; the connector only speaks A2A. (Contrast with LLM-bound bridges that wire in a specific provider such as OpenRouter — this one binds to none.)

Install

# Claude Code
claude mcp add a2a-connector -- uvx a2a-mcp-connector
# Codex
codex mcp add a2a-connector -- uvx a2a-mcp-connector

Any other MCP-aware client (Cursor, Claude Desktop, a hand-edited .mcp.json):

{
  "mcpServers": {
    "a2a-connector": {
      "type": "stdio",
      "command": "uvx",
      "args": ["a2a-mcp-connector"]
    }
  }
}

Before the package is published to PyPI, run it from a local checkout instead: uv run a2a-mcp-connector (from this directory) or uvx --from ./a2a-mcp-connector/dist/<wheel> a2a-mcp-connector.

Tools

bearer is optional — pass it only when the endpoint's card/RPC route requires auth. It is held in memory only and never logged or returned by any tool.

Flow

a2a_validate <card-url>            # optional pre-flight; a2a_connect validates anyway
a2a_connect  <card-url> <bearer?>  # start the session
loop:
  a2a_wait_turn                    # show the prompt to your human, get their reply
  a2a_send    <their reply>        # submit it
a2a_leave                          # when done (or "the session is over.")

The connecting agent should present each turn's prompt to its human and wait for their actual choice — it must not invent a reply.

How it works

One A2A task maps to the whole interaction. a2a_client.A2ASession resolves the Agent Card, derives the JSON-RPC URL from the served card path (reverse-proxy safe — it does not trust the card's advertised interface URL), opens or resumes the task, and drives turns with message/send. Because an A2A turn blocks until it is genuinely your turn, the session runs on one background asyncio task and the MCP tools are small, bounded polls over it — so a tool call never hangs.

validator.validate_agent_card fetches the raw card, parses it into the a2a-sdk AgentCard model (the authoritative "can this connector drive it?" check), then runs the standard-A2A structural checks (required fields, tolerant of both the supportedInterfaces and legacy top-level url shapes) and reports the capabilities.streaming capability.

Standalone

This package imports neither a2a_games nor a2a_raid_mcp (its game-specific sibling) — its only dependencies are the public mcp, a2a-sdk (pinned ==1.1.0), and httpx — so it is independently publishable to PyPI and reusable against any A2A endpoint.

License

MIT © 2026 Alvin Tay