Agent2Agent (A2A) Protocol
An open protocol enabling communication and interoperability between opaque agentic applications.
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- The repository contains only protocol documentation and CI configuration, with no executable code or tests, so its actual functionality cannot be verified.
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What does this agent do, and when should you use it?
Agent2Agent (A2A) is an open protocol that defines standard message formats and interaction flows, enabling AI agents built on different frameworks and by different vendors to communicate and collaborate. It addresses the lack of interoperability between AI agents, allowing them to work together as agents, not just as tools. The protocol is based on JSON-RPC 2.0 over HTTP(S), uses 'Agent Cards' for discovery, supports synchronous request/response, streaming (SSE), and asynchronous push notifications, and can exchange text, files, and structured data. The project is hosted under the Linux Foundation, with official SDKs for Python, Go, JS, and other languages, along with comprehensive documentation and samples. Adopting A2A provides agents with a common language, fostering a more interconnected, powerful, and innovative AI ecosystem.
A2A defines standardized mechanisms for agents to: 1) discover each other's capabilities by publishing 'Agent Cards' that detail capabilities and connection info; 2) negotiate interaction modalities including text, forms, and media; 3) securely collaborate on long-running tasks using task management methods (e.g., message/send, task/get, task/cancel), supporting synchronous, streaming, and asynchronous push patterns; 4) operate without exposing internal state, memory, or tools. The protocol itself is not an executable; it is implemented via SDKs (e.g., a2a-python, a2a-go, a2a-js) that provide libraries for developers to expose their agents as A2A servers or create clients to connect to other agents.
- A developer uses the Python SDK to expose a LangGraph-built agent as an A2A server, allowing other systems to invoke it.
- In a healthcare scenario, multiple agents built with different frameworks are connected via A2A to build a collaborative patient triage system.
- An enterprise IT team needs to integrate agents from multiple vendors; A2A serves as the standard for cross-vendor agent collaboration.
- A developer creates an A2A client to call a remote agent for a specific task, such as a customer service bot integrating a local order lookup agent.
- Using A2A's streaming and asynchronous push features to enable real-time conversations or progress notifications for long-running tasks.
What are this agent's strengths and limitations?
- Open, community-driven standard under the Linux Foundation, promoting multi-vendor collaboration.
- Provides official SDKs in multiple languages, lowering the barrier to adoption.
- Supports flexible interaction modes (synchronous, streaming, asynchronous) to suit different scenarios.
- Protocol design considers enterprise-grade security, authentication, and observability.
- Being a new protocol, the ecosystem is still early, with limited real-world deployments.
- Requires developers to learn a new protocol and SDKs, incurring a learning curve.
- Depends on network and HTTP services; not suitable for offline environments.
- Currently lacks dynamic method discovery (e.g., QuerySkill()), limiting flexibility and extensibility.
How do you install or deploy this agent?
A2A is a protocol specification; no installation is required. To use it, choose an SDK and install dependencies. Official SDKs include: Python SDK (pip install a2a-sdk), Go SDK (go get github.com/a2aproject/a2a-go), JS SDK (npm install @a2a-js/sdk), Java SDK (via Maven), .NET SDK (dotnet add package A2A), Rust SDK (cargo add a2a-lf). After installation, consult the official documentation and samples to learn how to implement A2A servers or clients.
How do you use this agent?
First, review the official documentation and protocol specification at https://a2a-protocol.org. Then, select the appropriate SDK for your language and follow the docs to create A2A-compliant agent servers or clients. Use the official samples (a2a-samples repository) to get started quickly. For example, with the Python SDK, you can import A2ARequestHandler and A2AServer from a2a.server, define your agent logic, and start the server.