A2A Protocol Development Guide

Overview

The A2A (Agent-to-Agent) protocol is a JSON-RPC based communication protocol designed for agent interactions. This guide provides comprehensive instructions for developing both server and client components that conform to the A2A protocol specification.

Protocol Basics

The A2A protocol is built on top of JSON-RPC 2.0 and defines a set of methods for agent communication. Key components include:

Message Structure

All A2A messages follow the JSON-RPC 2.0 format with a specific base structure:

interface JSONRPCMessage {
  jsonrpc?: "2.0";
  id?: number | string | null;
  method?: string;
  params?: unknown;
  result?: unknown;
  error?: JSONRPCError;
}

Protocol Flow

The protocol follows a specific interaction flow between client, server, and agent components.

Core Methods

The protocol supports several core methods:

`tasks/send`: Send a task message to an agent
`tasks/get`: Retrieve task status
`tasks/cancel`: Cancel a running task
`tasks/pushNotification/set`: Configure push notifications
`tasks/pushNotification/get`: Get push notification configuration
`tasks/resubscribe`: Resubscribe to task updates
`tasks/sendSubscribe`: Send a task message and subscribe to updates

Server Implementation

The server implementation consists of several key components:

Server (server.ts): Main server implementation
Handler (handler.ts): Request handler
Store (store.ts): Task storage and management
Utils (utils.ts): Utility functions
Error Handling (error.ts): Error definitions

Client Implementation

The client implementation provides key features for interacting with A2A servers:

JSON-RPC Communication
A2A Methods Implementation
Error Handling
Streaming Support
Extensibility

Running the Coder Demo

The Coder Demo is an example implementation of an A2A agent that can process code-related tasks. It demonstrates the practical application of the A2A protocol in a real-world scenario.

Error Handling

The A2A protocol defines several standard error codes for proper error handling and debugging.

Best Practices

Implement proper error handling
Use authentication mechanisms
Maintain task state management
Implement push notifications
Use comprehensive logging