Using A2A SDK

We built a complete A2A agent from scratch using FastAPI and raw JSON-RPC handling. That gave us a deep understanding of how A2A works behind the scenes: discovery endpoints, message structures, task life cycles, and protocol mechanics. Now, we’ll see how the official A2A SDK transforms that functionality into something more elegant, maintainable, and production-ready.

Think of our previous implementation as learning to drive a manual transmission; we learned exactly how the engine, clutch, and gears work together. Now, we’re upgrading to an automatic transmission that handles those details for you, so you can focus on where you want to go.

We’ll recreate the same echo agent, but this time, by using the official A2A Python SDK. The functionality will be identical: receive messages and echo them back, but you’ll see how much of the complexity is eliminated by the SDK. More importantly, this SDK version is ready for production with built-in error handling, observability, and extensibility.

What do we need to know before using the A2A SDK?

Before exploring the code, let’s understand the key components that make the A2A SDK powerful.

• AgentExecutor: Where your business logic lives. Instead of manually parsing JSON-RPC requests and constructing task objects, you implement execute() and cancel() methods that receive validated context and publish events.

• DefaultRequestHandler: Coordinates the entire request life cycle. It manages task creation, validates requests, calls your AgentExecutor, handles streaming, and constructs proper A2A responses.

• A2AFastAPIApplication: Replaces your manual FastAPI setup. It manages all A2A protocol details, including discovery endpoints, JSON-RPC routing, validation, error handling, and response formatting.

• InMemoryTaskStore: Manages task persistence and state. The SDK requires this to track task life cycles and history. ...