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

Governing Body Linux Foundation (A2A Project since June 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

Topology view

This tool in the centre and the things it is directly related to. Each line names the kind of relationship.

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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

Rich Text Editing

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

Local-First

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

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

Relationships

How this tool connects to other tools and organizations, from relationships reviewed by the OpenHaven data steward. They describe how projects connect, not how good they are.

Aims to interoperate with: ERC-8004