AI
A2A
An open protocol for communication between independent AI agents - discovery via a published Agent Card, work delegated as a stateful Task, updates streamed or pushed back.
Where MCP connects an agent to tools, A2A connects one agent to another - deliberately opaque, so neither side sees the other's internals. v1.0 added signed Agent Cards, per-interface versioning so v0.3 and v1.0 can be served side by side, and a versioned extension mechanism. It standardises the conversation, not the orchestration that chooses which agent to call.