A brief understanding of Google A2A agreement: This is not MCP!

Today Google released the A2A protocol (Agent-to-Agent Protocol), and I feel that many reports are inaccurate .

If you have the conditions, you can directly visit GitHub: https://github.com/google/A2A

Parameter definition: https://github.com/google/A2A/blob/main/specification/json/a2a.json

What is A2A?

A2A is an open communication protocol launched by Google, which aims to enable AI agents to communicate, collaborate, assign tasks, and synchronize results with each other.

The core problem it solves is: "How do multiple agents work together as a team?"

Imagine that you are a project manager (AI Agent A) and you assign another person (AI Agent B) to complete tasks, view progress in real time, and obtain results.

What does A2A define?

A2A provides a complete set of standardized interfaces and data structures, including:

✅Task  Initiation

Any Agent can tasks/send or tasks/sendSubscribe Send a task request to another Agent:

{
"method" : "tasks/send" ,
"params" : {
"id" : "task-123" ,
"message" : {
   "role" : "user" ,
   "parts" : [ {
     "type" : "text" ,
     "text" : "Please generate a project plan"
   } ]
    }
}
}

?  Task status tracking (Lifecycle & Streaming)

Tasks have a complete state lifecycle (such as:submitted → working → completed). If you use 
sendSubscribe, Agents can subscribe to SSE (Server-Sent Events) to receive status updates:

{ 
"state" : "working" ,  
"timestamp" : "2025-04-10T12:00:00Z"  
}

You can also set up a Webhook to automatically push back task progress.

?  Get results (Artifacts)

After the task is completed, the executor returns a artifact object, which contains several part Content units (text, structured data, files, etc.):

{
  "artifact" : {
    "parts" : [
      {
        "type" : "text" ,
        "text" : "The project plan is as follows..."
      }
    ]
}
}

?  Agent Capability Exposure (AgentCard)

Each Agent needs to provide a standard capability description file /.well-known/agent.json, used for discovery and access. It contains:

• • Supported methods
• • Authentication method
• • Input and output formats
• • Whether streaming/push is supported, etc.

?  Summary

How to use A2A

1. 1.  Discover the other party's Agent (through agent.json)
2. 2.  Initiate a task (send / sendSubscribe)
3. 3.  Subscribe to status stream/wait for synchronization return
4. 4.  Obtain results/interactive supplement
5. 5.  Complete or fail

What is MCP?

MCP (Model Context Protocol) is a protocol proposed by Anthropic that allows AI models to connect to various tools and data sources.

It's like a person opening a tool box and taking out the tools he needs to do the work.

It solves:

• •  Connect external tools : Give the external interface an API Call
• •  Get external data : Access external content such as databases, documents, APIs, web pages, etc. as context

Relationship between A2A and MCP

These two have absolutely nothing to do with each other!!!

A2A is AI  "I command you to do the work"

• • For example: "Write a report and tell me when you're done."
• • More like collaboration and division of labor within a team

MCP is AI  "I do the work myself, and the tools assist me"

• • For example: "I'll check the sales records in the database"
• • More like a person solving a problem with tools