A2A-RMCP Integration

A bridge between Agent-to-Agent (A2A) protocol and Rusty Model Context Protocol (RMCP)

Overview

This crate provides integration between the A2A protocol and RMCP, enabling bidirectional communication between these protocols. It follows a bridge pattern with adapter layers for message conversion and protocol translation.

Key Features

Use A2A agents as RMCP tools
Expose RMCP tools as A2A agents
Bidirectional message conversion
State management across protocols

Examples

Both run end-to-end with no external setup — they wire up the A2A and MCP sides in-process over an in-memory duplex transport.

cargo run --example a2a_as_mcp_server -p a2a-mcp — spins up a tiny A2A HTTP agent, bridges it with AgentToMcpBridge, and demonstrates an MCP client listing and calling its tools.
cargo run --example a2a_with_mcp_tools -p a2a-mcp — wraps an A2A handler with McpToA2ABridge so TOOL_CALL: <name> messages get routed to an in-process MCP server.

Architecture

flowchart TD
    subgraph A2A[A2A Protocol]
        A2AAgent[A2A Agent]
        A2AClient[A2A Client]
    end

    subgraph Bridge[a2a-mcp Bridge]
        A2AMCPBridge[AgentToMcpBridge\n(A2A Agent as MCP Server)]
        MCPA2ABridge[McpToA2ABridge\n(MCP Server as A2A Agent)]
        
        A2AMCPBridge <--> |MessageConverter| Converters
        MCPA2ABridge <--> |MessageConverter| Converters
    end

    subgraph MCP[MCP Protocol]
        MCPClient[MCP Client]
        MCPServer[MCP Server]
    end

    A2AAgent <--> |A2A Messages| A2AMCPBridge
    A2AMCPBridge <--> |MCP JSON-RPC| MCPClient
    
    A2AClient <--> |A2A Messages| MCPA2ABridge
    MCPA2ABridge <--> |MCP JSON-RPC| MCPServer

Development Status