Definition
Google announced the Agent2Agent (A2A) protocol in April 2025 with a large group of technology partners, and later contributed it to the Linux Foundation. Where MCP connects an agent to tools and data, A2A connects agents to other agents.
Each A2A agent publishes an 'agent card' describing what it can do. A client agent can then send it a task, follow progress and receive results, even when the two agents run on different platforms. The goal is interoperability across the many agent platforms that large organisations end up running side by side.