# Agent2Agent Protocol A2A

[6 · Coordinate](/category/coordinate/)

| Agent2Agent Protocol |
| --- |
| Category | [Coordinate](/category/coordinate/) |
| Governed by | Linux Foundation (A2A Project); contributed by Google |
| Status | Stable, v1.0.0 |
| Phase | stable |
| Implementation | multi-implementation |
| Adoption | claimed — Linux Foundation |
| Version | 1.0.0 (2026-01) |
| Specification | [https://a2a-protocol.org/latest/specification/](https://a2a-protocol.org/latest/specification/) |
| Found at | /.well-known/agent-card.json |
| Acronym collisions | Account-to-Account payments (A2A, banking) |
| Last checked | 2026-09-06 |

[Coordinate](/category/coordinate/) Agent2Agent (A2A) is an open protocol for two independent AI agents — potentially built on different frameworks, by different companies, running on separate servers — to discover each other's capabilities and collaborate on a task without either exposing its internal memory, tools, or proprietary logic [[1]](#ref-1). It solves agent-to-agent interoperability at the application layer: an A2A server publishes a JSON "Agent Card" describing its identity, service endpoint, supported interaction modes (sync request/response, Server-Sent Events streaming, async push notifications), and skills; a client agent fetches that card, then exchanges JSON-RPC 2.0 messages over HTTP(S) to create and drive a task to completion [[1]](#ref-1). Standard discovery is the well-known URI https://{domain}/.well-known/agent-card.json, per RFC 8615; the spec also allows curated-registry discovery (no standard registry API is prescribed) and direct/hardcoded configuration [[1]](#ref-1).

## Overview
A2A does not itself define a registry protocol, a payment mechanism, or a UI-rendering format — those are left to other layers (registries, x402/agentic-commerce specs, and UI-negotiation extensions respectively). It also does not replace intra-agent tool-calling protocols such as MCP; A2A and MCP are commonly described by the project as complementary.

Google announced A2A on 2025-04-09 with 50+ launch partners and donated it to the Linux Foundation later in 2025 [[2]](#ref-2). The specification reached v1.0.0 and is now labeled stable on the project's own documentation site [[1]](#ref-1). At its one-year mark (2026-04-09) the project's press release claimed more than 150 supporting organizations, integration into major cloud platforms (the release names Google Cloud, Microsoft, and AWS), and active production deployments in supply chain, financial services, insurance, and IT operations [[3]](#ref-3) — this adoption count is a claim by the Linux Foundation/A2A project itself, not an independently measured probe count, so it is recorded here as "claimed," not "measured."

Official SDKs are published for Python, Go, JavaScript, Java, .NET, and Rust under the a2aproject GitHub organization, and the project lists integrations from frameworks including Google ADK, LangGraph, and IBM's BeeAI [[2]](#ref-2). What remains open/disputed: the spec explicitly does not standardize a registry API for curated discovery, leaving that to individual deployments; and no third-party, methodology-disclosed count of live A2A servers (as opposed to "supporting organizations") was found as of this verification pass.

## Discovery and probe

Agent Card · /.well-known/agent-card.json

```
GET {origin}/.well-known/agent-card.json
parse:     JSON body with name, url (A2A service endpoint), and skills[] fields present confirms an A2A server
on absent: 404 or non-JSON response means no public Agent Card is hosted at this well-known path; the origin may still run A2A behind auth or a registry
```

Live check run by [the MCP probe](/mcp/server-card): GET /.well-known/agent-card.json. An A2A Agent Card names the agent and its service URL.

```
{
 "path": "/.well-known/agent-card.json",
 "expect": {
  "content_type": "json",
  "json_keys": [
   "name",
   "url"
  ]
 },
 "note": "An A2A Agent Card names the agent and its service URL."
}
```

## History
- 2026-09-05 — seeded from Exa Agent research run
- 2026-09-06 — verified against a2a-protocol.org/latest/specification/, github.com/a2aproject/A2A README and agent-discovery.md, and the LF/A2A one-year press release (prnewswire)

## Instances

- [a2a-rs (Rust)](https://github.com/a2aproject/a2a-rs) · Observed 2026-09-05 · service
- [a2a-python (reference SDK)](https://github.com/a2aproject/a2a-python) · Observed 2026-09-05 · service
- [a2a-js](https://github.com/a2aproject/a2a-js) · Observed 2026-09-05 · service
- [a2a-java](https://github.com/a2aproject/a2a-java) · Observed 2026-09-05 · service
- [a2a-go](https://github.com/a2aproject/a2a-go) · Observed 2026-09-05 · service
- [a2a-dotnet](https://github.com/a2aproject/a2a-dotnet) · Observed 2026-09-05 · service
- [Salesforce (Agentforce)](https://www.salesforce.com/agentforce/) · Observed 2026-05-20 · business
- [Microsoft (Azure AI Foundry / Copilot Studio)](https://azure.microsoft.com/en-us/products/ai-foundry) · Observed 2026-05-20 · business
- [ServiceNow](https://www.servicenow.com) · Observed 2026-04-24 · business
- [SAP](https://www.sap.com) · Observed 2026-04-24 · business
- [AWS Bedrock AgentCore Runtime](https://aws.amazon.com/bedrock/agentcore/) · Observed 2026-04-09 · service
- [150+ supporting organizations (claimed by the A2A project at its one-year mark)](https://www.prnewswire.com/news-releases/a2a-protocol-surpasses-150-organizations-lands-in-major-cloud-platforms-and-sees-enterprise-production-use-in-first-year-302737641.html) · Observed 2026-04-09 · business

Every instance with its source is listed on the [instances page](/instances/).

## See also

- [Agent Card](/terms/agent-card/)
- [Well-known URI](/terms/well-known/)
- [Agentic web](/terms/agentic-web/)

- Not to be confused with: Account-to-Account payments (A2A, banking)

## References

- A2A v1.0.0 specification defines JSON-RPC 2.0 over HTTP(S), the Agent Card discovery document, and the well-known path /.well-known/agent-card.json per RFC 8615. — [https://a2a-protocol.org/latest/specification/](https://a2a-protocol.org/latest/specification/) (2026-09-05) VERIFIED
- The A2A Protocol project is an open source project under the Linux Foundation, contributed by Google, licensed Apache 2.0. Official SDKs exist for Python (a2a-sdk), Go, JavaScript, Java, .NET, and Rust, maintained under the a2aproject GitHub org. — [https://raw.githubusercontent.com/a2aproject/A2A/main/README.md](https://raw.githubusercontent.com/a2aproject/A2A/main/README.md) (2026-09-05) VERIFIED
- On its one-year anniversary (announced 2026-04-09), the A2A Protocol project stated it had surpassed 150 supporting organizations and cited integration in major cloud platforms and enterprise production use. — [https://www.prnewswire.com/news-releases/a2a-protocol-surpasses-150-organizations-lands-in-major-cloud-platforms-and-sees-enterprise-production-use-in-first-year-302737641.html](https://www.prnewswire.com/news-releases/a2a-protocol-surpasses-150-organizations-lands-in-major-cloud-platforms-and-sees-enterprise-production-use-in-first-year-302737641.html) (2026-04-09) VERIFIED

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