A2A (Agent2Agent)

P2P Protocol

Open protocol standard enabling interoperability between independent AI agents across organizational boundaries, frameworks, and vendors. Defines AgentCards (JSON capability advertisements), task lifecycle management, and JSON-RPC 2.0 over HTTP/HTTPS with SSE streaming. Agents discover each other's capabilities, negotiate interaction modalities, and collaborate on tasks without exposing internal state, memory, or tools. Designed to complement MCP (MCP connects agents to tools; A2A connects agents to agents). Originated at Google April 2025; donated to Linux Foundation June 2025; 150+ supporting organizations.

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Details

License Open source — Apache 2.0; GitHub: github.com/a2aproject/A2A
Dev Status 🟢 Active
Dev Status Detail Production / Active development — specification v0.3 released; gRPC support added; SDKs in Python and TypeScript; 150+ supporting organizations
Owner Linux Foundation (A2A Project, since June 23, 2025); originally created by Google
Country USA
Start Year 2025
Stack Language-agnostic specification; SDKs in Python, TypeScript; compatible with LangGraph, CrewAI, Google ADK, BeeAI, Semantic Kernel
Funding Linux Foundation (neutral governance); Google (originator)
Last Investigated Jan 15, 2026

Use Case Domains

Co-Creation & Knowledge Events & Coordination

Affordances

Interoperable formats

P2P Protocol Attributes

Origins Google's internal experience running large multi-agent enterprise systems; identified need for standardized agent discovery, authentication, and task orchestration across vendor boundaries without custom integration per connection
Database N/A — stateless message protocol
Query Language N/A
Data Formats JSON (AgentCard, Task, Message payloads); JSON-RPC 2.0; SSE (Server-Sent Events) for streaming
Collaborative Live Editing No
Rich Text Editing No
Mobile Support Yes (HTTP-compatible mobile clients)
Web Support Yes (HTTP/HTTPS native)
Native Apps Yes
Terms Apache 2.0
Funds N/A (corporate-originated; Linux Foundation hosted)
Based On JSON-RPC 2.0; OAuth 2.0 / OIDC / API Keys / mTLS (authentication); MCP (complementary protocol — MCP for tools, A2A for agents); ERC-8004 (planned integration for agent identity and trust)
P2P Architecture Client-server (A2A Client delegates tasks to A2A Server/remote agent); not a mesh topology
Overlay Network N/A — HTTP endpoint discovery via AgentCard URL
Content Addressing No
Local-First No
E2EE Yes — HTTPS with TLS required in production; agent internal state not exposed to peers
CRDTs Lib N/A
Byzantine Fault Tolerance N/A — no distributed consensus; task lifecycle managed by individual agents
Signature Yes — OAuth 2.0 / OIDC tokens; signed AgentCards (v0.3+); mTLS
Permissions OAuth 2.0 / OIDC (token-based); API Key; mTLS
Semantic Web Compatibility No
Smart Contract No (protocol layer; no smart contract component)
Protocol Stack Position Application-layer (built on HTTP/HTTPS)
Asset / Value Embedding None — A2A is a communication protocol; value/payment handled by complementary protocols such as x402
Protocol Maturity / Standardization Production / Linux Foundation Open Standard — v0.3 specification released; 150+ supporting organizations including AWS, Cisco, Microsoft, Salesforce, SAP, ServiceNow; Apache 2.0; not yet submitted to IETF or W3C