What is A2A (Agent to Agent) Protocol
Learn what the A2A Agent to Agent protocol is, how it compares to MCP and ACP, and how to build narrow agents with explicit message contracts, streaming, and metrics
The A2A protocol is a standards-based way for AI agents to discover each other, describe what they can do, exchange tasks and messages, and report results in a predictable lifecycle. It gives teams a shared contract for agent interoperability so you can plug a capable agent into different clients and ecosystems without rebuilding custom adapters for every integration.
In practice, you define an agent card that advertises capabilities and contact details, you agree on message shapes and status transitions, and you use common transports like HTTP with streaming for long-running work.
When I took training at work on agent-to-agent communication protocols, my lightbulb moment was realizing our service did not need a Model Context Protocol server that only exposes tools. We needed an autonomous agent that can accept a task, maintain state, and collaborate with other agents through a standard contract. That pushed me toward learning more about A2A because it treats the remote side as a peer …