An open protocol enabling communication and interoperability between opaque agentic applications.

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What is A2A Protocol?

The Agent2Agent (A2A) Protocol is an open standard for seamless communication and collaboration between AI agents. In a world where agents are built using diverse frameworks and by different vendors, A2A provides the definitive common language for agent interoperability.

Build with ADK (or any framework), equip with MCP (or any tool), and communicate with A2A, to remote agents, local agents, and humans.

Key Features

• Interoperability

  Connect agents built on different platforms (LangGraph, CrewAI, Semantic Kernel, custom solutions) to create powerful, composite AI systems.

• Complex Workflows

  Enable agents to delegate sub-tasks, exchange information, and coordinate actions to solve complex problems that a single agent cannot.

• Secure & Opaque

  Agents interact without needing to share internal memory, tools, or proprietary logic, ensuring security and preserving intellectual property.

• Extensible

  Add capabilities through formal protocol extensions and custom bindings, governed by a tiered promotion process so the core stays stable.

Get started with A2A

• Read the Introduction

  Understand the core ideas behind A2A.

  What is A2A?

  Key Concepts

• Dive into the Specification

  Explore the detailed technical definition of the A2A protocol.

  Protocol Specification

• Follow the Tutorials

  Build your first A2A-compliant agent with our step-by-step Python quickstart.

  Hands-on-Tutorial

• Explore Code Samples

  See A2A in action with sample clients, servers, and agent framework integrations.

  GitHub Samples

• Download the Official SDKs

  Python

  JavaScript

  Java

  C#/.NET

  Golang

  Rust

• Video Intro in under 8 min

• Course DeepLearning.AI - Intro to A2A

  

How A2A Works with MCP

The Model Context Protocol (MCP) and the A2A Protocol are not competitors — they are highly complementary. They solve two different problems and are designed to work together.

• MCP is for agent-to-tool communication: it standardizes how an agent connects to its tools, APIs, and resources to get information. See Model Context Protocol.
• A2A is for agent-to-agent communication: as a universal, decentralized standard, A2A lets independent agents — including those using MCP — discover each other, delegate tasks, and share results.

Use MCP to equip an individual agent with the specific tools it needs to do its job (e.g., access to a GitHub repository or a SQL database). Use A2A to let that specialized agent securely collaborate with other agents across different frameworks.

flowchart LR
    User(🧑‍💻 User) <--> ClientAgent(🤖 Client Agent)
    RemoteAgent(🤖 Remote Agent)
    RemoteTool(⚙️ Remote Tool)
    ClientAgent -- Using <img src="assets/a2a_logo/icon/color/SVG/a2a_icon_color.svg" alt="Agent2Agent Protocol Logo" height="40" width="40"> --> RemoteAgent
    ClientAgent -- Using <img src="https://modelcontextprotocol.io/mcp.png" alt="Agent2Agent Protocol Logo" height="40" width="40"> --> RemoteTool


    style User fill:#fdebd0,stroke:#e67e22,stroke-width:2px
    style ClientAgent fill:#d6eaf8,stroke:#3498db,stroke-width:2px
    style RemoteAgent fill:#d6eaf8,stroke:#3498db,stroke-width:2px
    style RemoteTool fill:#d6eaf8,stroke:#3498db,stroke-width:2px

A2A and MCP — deeper dive

What A2A Is Not

A2A is a focused protocol. To set expectations, here is what it explicitly does not try to be:

• Not an agent development kit like LangGraph, CrewAI, or ADK for building agentic applications. A2A is the communication layer between agents built with any of these.
• Not a sub-agent or tool-call protocol. A2A does not specify how an agent talks to its own sub-agents or how it invokes tools — use your framework's native primitives, or MCP, for those.
• Not a replacement for MCP. MCP standardizes agent-to-tool communication; A2A standardizes agent-to-agent communication. They are complementary (see above).
• Not an interactive messaging app like Slack, Discord, WhatsApp, or Telegram. A2A is a machine-to-machine protocol for autonomous agents.

Governance & Open Source

A2A was originally developed by Google and donated to the Linux Foundation. It is maintained by a Technical Steering Committee with representatives from AWS, Cisco, Google, IBM Research, Microsoft, Salesforce, SAP, and ServiceNow, and supported by a broad community of partners.

For details on how the project is run, see GOVERNANCE.md and MAINTAINERS.md.

License

The A2A Protocol is licensed under the Apache License 2.0 and welcomes contributions from the community.