# Agent2Agent (A2A) Protocol

> An open interoperability layer for agent-to-agent communication: it lets independent agents discover each other, exchange capabilities, and coordinate tasks. It is not a payment-execution protocol itself — payments ride on top via other protocols.

## At a glance

| Field | Value |
| --- | --- |
| Name | A2A |
| Layer | agent-communication |
| Category | framework |
| Status | live |
| Created by | Google |
| Launched | 2025-04 |
| Rails | — |
| Settlement | — |
| Reversible | — |
| Human in loop | — |
| D2C fit | — |
| B2B fit | — |
| Spec | https://a2a-protocol.org/latest/ |
| Last verified | 2026-09-02 |

## How it works

A2A is a **communication and interoperability standard**, not a payment rail. Its purpose is to let agents built by different vendors, on different frameworks, **discover one another and collaborate** on tasks.

- **Agent Cards.** Each agent publishes a machine-readable descriptor advertising its identity, skills, and endpoints, so a client agent can find and evaluate a remote agent.
- **Tasks & messages.** A client agent opens a task with a remote agent and they exchange structured messages and artifacts until the task completes, supporting long-running and streaming interactions.
- **Transport.** It layers on ordinary web primitives (HTTP, JSON-RPC/SSE), which keeps it framework-agnostic and easy to adopt alongside existing services.

The most common point of confusion is treating A2A as a way to *pay* agents. It is not: A2A carries the **coordination**, and value transfer is delegated to a dedicated payment or authorization layer (for example AP2 for mandates, or an execution protocol such as x402). Keeping this distinction explicit is essential when reading the comparison matrix — the settlement and reversibility columns are marked not-applicable for A2A on purpose.

## Tradeoffs

- Carries no payment semantics: any monetary exchange must be delegated to a separate authorization/execution protocol.
- Interoperability depends on both agents adopting the same version and honoring published Agent Card capabilities.
- As a coordination layer, it inherits the trust and identity problems of whichever agents connect through it.

## Security & limitations

- Agent discovery and capability advertisement widen the surface for impersonation and capability spoofing without strong agent identity.
- Because tasks can be long-running and delegated, injection or manipulation mid-task can propagate to downstream systems the agent can reach.

## Fits together with

- ap2
- x402

## Sources

1. [A2A Protocol — documentation](https://a2a-protocol.org/latest/) — A2A Project
2. [A2A: A new era of agent interoperability](https://developers.googleblog.com/en/a2a-a-new-era-of-agent-interoperability/) — Google Developers Blog, 2025-04
3. [A2A specification and reference material](https://github.com/a2aproject/A2A) — A2A Project (GitHub)

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_Source: payful.ai — independent editorial reference. Verified 2026-09-02._