Agent2Agent (A2A)

Coordinate Agent2Agent (A2A) is an open protocol—launched by Google in April 2025 and stewarded by the Linux Foundation Agentic AI Foundation (AAIF)—for peer-to-peer communication and task delegation between opaque autonomous agents across organizational boundaries. Where MCP connects a host model to tools and data sources (Step 5: Act), A2A coordinates multi-turn, potentially long-running Tasks between independent agents (Step 6: Coordinate) that discover each other via /.well-known/agent-card.json, exchange typed Part messages and output Artifact objects, and stream updates over SSE or webhook push notifications without exposing internal memory or prompts. Used by: a2a.