WTF is A2A? (Agent2Agent Protocol)
An open protocol for AI agents built by different vendors to discover each other and hand off work.
Also called: agent2agent, agent-to-agent protocol
TL;DR
MCP connects an agent to tools; A2A connects an agent to other agents. It gives agents a common way to say "here's what I can do" and "please do this task for me", even when they run on different frameworks or companies' platforms.
How it works
Each A2A agent publishes an Agent Card (JSON metadata describing its skills, endpoint and auth). A client agent sends tasks to a remote agent over HTTP using JSON-RPC, and the remote agent returns messages and artifacts, optionally streaming progress. Tasks have a lifecycle (submitted, working, input-required, completed), which allows long-running and human-in-the-loop work across agent boundaries.
Origin
- Coined / introduced by
- When
- 9 Apr 2025
- Story
- Announced by Google with a coalition of partners, later moved to open governance.