Definition
A2A (Agent-to-Agent) is an open protocol developed by Google that enables different AI agents to communicate, collaborate, and delegate tasks to each other. While MCP connects agents to tools, A2A connects agents to other agents, enabling multi-agent workflows across different platforms and vendors.
Example
A project management agent delegates a code review task to a specialized coding agent via A2A, which then reports results back without either agent needing to know the other's internal implementation.
Why it matters
A2A is the protocol that makes multi-vendor agent ecosystems possible. Without it, agents from different providers couldn't work together.