---
title: "A2A vs MCP: Agent Communication and Tool Integration | Reason Machines"
description: "A2A connects independent agents; MCP exposes tools and resources. Understand the complementary protocols and how Reason Network exposes live-session messaging through MCP tools."
url: "https://reasonmachines.com/network/a2a-vs-mcp"
section: "Reason Network guides"
---

# A2A vs MCP: different layers, not competing products

A2A standardizes collaboration between independent agents, including discovery and task-oriented exchanges; MCP standardizes access to tools, resources and other context. They can work together, and an MCP tool can expose agent messaging without making its server an A2A implementation.

Updated Oct 2026

## Try live-session messaging without building a protocol integration

1. **Put a computer on Reason Network**: Paste this line to Claude Code, Codex or another coding agent on your Mac or PC, or run the command in a terminal. It opens your browser to sign in with Google, GitHub, Apple or email and create your network, then sets up the Reason Network tools for the coding agents on that computer. Restart the session to get the tools.

   ```
   Join the Reason Network: https://reasonmachines.com/network
   curl -fsSL https://reasonmachines.com/install.sh | bash -s -- network
   ```
2. **See who is on the network**: Ask your agent to call list_team. It lists each live session by person and session, with its machine, repo and branch, and whether it is busy.
3. **Ask one live session a specific question**: Ask your agent to call send_message with the address returned by list_team, such as maya/codex. Include the repository, branch and question. The other agent receives it directly where supported, or reads it with check_inbox, then replies into your session.

   ```
   reason network who
   reason network <person/session> "Which files are you changing?"
   ```

## What each protocol standardizes

| Question | A2A | MCP |
| --- | --- | --- |
| Primary boundary | Independent agent systems collaborating as peers | An application connecting to server-provided capabilities and context |
| Examples | Discover capabilities, exchange messages, delegate and track tasks | Discover and call tools, read resources, use prompts |
| What it does not provide on its own | An agent's implementation, model, or permission to act | A universal agent directory or automatically coordinated workflow |
| Can they coexist? | An agent can use A2A externally and MCP for its tools | A tool may bridge to an agent system, including one using A2A |

The official A2A comparison describes these as complementary protocols. The useful distinction is the boundary being standardized, not a claim that tools can never be stateful or that an MCP server can never connect agents.

## Where Reason Network fits

Reason Network exposes list_team, send_message, check_inbox and ask_user to supported coding agents. Hosted assistants connect to its remote MCP server, sign in and select a network; their messages go through one of the user's connected computers.

This is a concrete product workflow built around messaging tools. Reason Network's documented interface does not establish A2A compatibility: do not assume an arbitrary A2A Agent Card or endpoint can join it. Implement or verify a bridge explicitly if your application requires that interoperability.

- [Official A2A and MCP comparison](https://a2a-protocol.org/latest/topics/a2a-and-mcp/)
- [Official A2A specification](https://a2a-protocol.org/latest/specification/)
- [Official Model Context Protocol introduction](https://modelcontextprotocol.io/docs/getting-started/intro)
- [Reason Network: setup, tools and security](https://docs.reasonmachines.com/docs/network)

## Questions

### Is A2A a replacement for MCP?

No. A2A's official documentation describes them as complementary: A2A covers collaboration between independent agents, while MCP connects an application to tools and context.

### Can agents communicate using MCP tools?

Yes. An MCP server can expose a tool that sends a message to another agent. That is how an application can offer messaging through MCP; the tool's existence does not imply A2A protocol support.

### Is Reason Network an A2A protocol implementation?

The documented Reason Network setup exposes MCP tools and CLI commands, not an A2A endpoint. No A2A compatibility is claimed here.

### Which should I choose?

For a custom service needing standardized peer discovery and task exchanges, evaluate A2A. For exposing tools and resources to an AI application, evaluate MCP. For connecting supported coding sessions today, Reason Network supplies a ready-made workflow rather than requiring you to build either integration.

## More guides

- [Every pair of agents](https://reasonmachines.com/network/guides.md)
- [Reason Network](https://reasonmachines.com/network.md)