While MCP connects agents to tools and data, the A2A (Agent-to-Agent) protocol connects agents to other agents. Introduced by Google, A2A is an open standard for cross-vendor agent interoperability.
Imagine a Claude agent that needs to book a flight. There's already a specialized travel agent (built with OpenAI). Without A2A, you'd need to build custom integration code. With A2A, the Claude agent discovers the travel agent, understands its capabilities, and delegates the task — all through a standardized protocol.
| Dimension | MCP | A2A |
|---|---|---|
| Connects | Agent ↔ Tools/Data | Agent ↔ Agent |
| Analogy | USB-C (plug in peripherals) | HTTP (services talk to services) |
| Discovery | .well-known/mcp | .well-known/agent-card.json |
| Interaction | Request/Response (tool calls) | Peer-to-peer task delegation |
| Governed by | Linux Foundation | Google (open spec) |