A2A Protocol

Overview

MCP exposes tools to an agent. A2A connects agents to agents. The 2026 Linux Foundation AAIF specification standardizes capability cards, task envelopes, and the negotiation handshake — so a Claude agent can hand work to a Codex agent (or a third-party vendor agent) without bespoke glue.

When to use

• Two agents need to collaborate across runtime/vendor boundaries
• You're tired of writing custom HTTP wrappers between agent systems
• Cross-org agent collaboration (your billing agent ↔ vendor support agent)
• Mesh / federated agent systems

Don't use when

• Both agents share a runtime (just call a function or use orchestrator)
• One-direction tool call → use MCP (mcp-server-design)

Core concepts