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Agent-to-Agent Protocol (A2A)

protocol
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Agent-to-Agent (A2A) is an open, HTTP-based protocol that enables AI agents—built on different frameworks to coordinate tasks, exchange information, and collaborate. Backed by companies like Google, Salesforce, and LangChain, A2A standardizes inter-agent communication and discovery, preparing the way for modular, scalable multi-agent systems. This protocol is especially suitable when agents must operate independently but collaborate via clearly defined interfaces.

While MCP standardizes LLM-to-environment interaction, A2A focuses on agent-to-agent coordination. These protocols are complementary: MCP enables agents to reason with tools and context, while A2A enables those agents to talk to each other.

Key Concepts

  • A2A introduces three core actors: User (initiates requests), A2A Client (that makes requests on the user's behalf) and A2A Server (remote agent that fulfills requests and returns results)
  • AgentCard: JSON descriptor of an agent’s identity, capabilities, skills, endpoint, and auth requirements.
  • Discovery: Agents can be found via .well-known URLs, registries, or static configuration.
  • Communication: JSON-RPC over HTTP(S) using tasks and artifacts. Supports:
    • Synchronous (sendTask)
    • Asynchronous polling
    • Streaming (SSE)
    • Push (webhooks)
  • Security: AgentCard-defined auth schemes (API keys, OAuth2)

Resources