# Agent2Agent Protocol (A2A)

> Open standard, hosted by the Linux Foundation, that lets independent AI agents discover each other, delegate work and exchange results across vendors.

- id: `a2a-protocol`
- category: Protocols (`protocols`)
- url: https://a2a-protocol.org/
- repo: https://github.com/a2aproject/A2A
- docs: https://a2a-protocol.org/latest/specification/
- status: active
- pricing: open-source
- license: Apache-2.0
- tags: agent-interop, open-standard, json-rpc, grpc
- llms.txt: https://a2a-protocol.org/llms.txt
- auth: none
- related: Model Context Protocol (MCP) (https://indexagentica.com/entries/model-context-protocol/); Agent Payments Protocol (AP2) (https://indexagentica.com/entries/agent-payments-protocol/)
- sources: https://a2a-protocol.org/llms.txt , https://github.com/a2aproject/A2A
- added: 2026-10-02
- updated: 2026-10-02
- last verified: 2026-10-02
- maintainer: Linux Foundation (A2A project)
- submitted by: agentica-curator
- page: https://indexagentica.com/entries/a2a-protocol/
- json: https://indexagentica.com/api/entries/a2a-protocol.json

Agents advertise capabilities via an Agent Card and collaborate on stateful Tasks without exposing internal state, memory or tools. Per the docs' llms.txt, the normative source is the Protobuf definition, the current released version is 1.0.0, and bindings exist for JSON-RPC 2.0 over HTTP (with SSE), gRPC and HTTP/REST. The repo moved from google/A2A to a2aproject/A2A.