Communication Between Agents › Real-World Communication: The A2A Protocol

Earlier we discussed the Agent-to-Agent (A2A) Protocol as a framework for multi-agent systems. Now let's look specifically at how A2A handles communication.

A2A defines standard message formats and communication patterns that work across different platforms. When agents use A2A, they can communicate even if one is built with Claude, another with GPT-5, and a third with Gemini.

Key A2A Communication Features:

Agent Discovery: Agents can find other agents by querying a registry. "Are there any research agents available?" returns a list of agents with their capabilities.

Capability Negotiation: Before communicating, agents can check if they speak compatible "languages." Agent A can ask Agent B: "Do you accept JSON input?" or "Can you return image data?"

Standardized Message Envelope: All A2A messages include metadata (sender, recipient, timestamp, message type) in a consistent format, similar to our AgentMessage class but with additional fields for authentication and routing.

Task Lifecycle Management: A2A includes built-in protocols for task delegation, progress tracking, and completion, similar to our TaskDelegationProtocol but standardized across all A2A-compatible agents.

Error Handling: A2A defines standard error codes and formats, so agents can understand what went wrong even across different implementations.

While we won't implement the full A2A protocol here (it's complex and still evolving), the patterns we've explored in this chapter align with A2A's design principles. When you build multi-agent systems, following similar patterns will make your agents more interoperable and maintainable.