What is A2A (Agent-to-Agent Protocol)?

Published: May 21, 2026

A2A (Agent-to-Agent) is Google's open protocol for AI agents to find each other, understand what each can do, and communicate. It was released in early 2025 and solves a straightforward problem: as AI agents multiply, they need a standard way to work together without custom integration code between every pair.

Why A2A exists

A travel booking agent might need to call a payment agent, a calendar agent, and a flight search agent. Without a standard, each of those connections requires custom code. A2A provides a universal discovery and communication layer so any A2A-compatible agent can find and talk to any other.

How it works

1. Agent Cards (how agents advertise themselves)

An Agent Card is a JSON file at /.well-known/agent.json on your domain. It describes what your agent can do, how to authenticate, and what actions it supports.

{
  "name": "My Service Agent",
  "description": "Handles booking and scheduling",
  "url": "https://myservice.com",
  "capabilities": ["booking", "scheduling"],
  "authentication": {
    "type": "bearer"
  }
}

Any agent that finds your Agent Card knows immediately whether you can help with a given task.

2. Task communication

Once discovered, agents communicate through standardized task objects. A requesting agent sends a task description. Your agent processes it and returns results. No custom API contract needed on either side.

Who needs an Agent Card

• Any service with an API that AI agents might want to use
• Businesses that want to be discoverable as the agent ecosystem grows
• Developers building AI agents that need to advertise their capabilities

You do not need a full agent implementation to start. Publishing an Agent Card makes your service discoverable now, so you are ready when agent-to-agent traffic becomes significant.

A2A vs MCP

These two protocols are complementary:

• MCP connects an AI model to tools and data sources (model to tool)
• A2A connects AI agents to other agents (agent to agent)

A service might use MCP to let AI query its database, and A2A to let other agents discover and request its services. They operate at different layers.