# ACP

> A REST-native alternative to A2A for teams that want inter-agent messaging over plain HTTP with minimal new machinery.

_The Agent Protocol Atlas · /protocols/acp · [JSON](/api/protocols/acp) · [all The Agent Protocol Atlas](/protocols)_

- **name:** ACP
- **full_name:** Agent Communication Protocol
- **layer:** interop
- **creator:** IBM / AGNTCY
- **status:** emerging
- **year:** 2025
- **one_liner:** A REST-native alternative to A2A for teams that want inter-agent messaging over plain HTTP with minimal new machinery.
- **spec_url:** https://agentcommunicationprotocol.dev
- **snippet:**

```
POST /agents/{id}/runs  { "input": [ ... ] }  // ordinary REST, no special transport
```
- **abbreviation:** ACP
- **also_known_as:** Agent Communication Protocol
- **canonical_spec_url:** https://agentcommunicationprotocol.dev
- **entity_uri:** https://agentcommunicationprotocol.dev
- **taxonomy_layer:** interop
- **sub_layer:** agent-to-agent
- **protocol_type:** transport
- **central_problem:** Provides inter-agent messaging over ordinary REST/HTTP so teams can connect agents without adopting a new transport or RPC layer.
- **maintainer:** IBM / AGNTCY community (Linux Foundation AGNTCY initiative)
- **governance_body:** AGNTCY / Linux Foundation
- **license:** Apache-2.0
- **maturity_tag:** emerging
- **current_spec_version:** — (verify-against-primary-at-build)
- **spec_date:** — (verify-against-primary-at-build)
- **launch_date:** 2025
- **last_verified:** 2026-06-15
- **transport:** REST over HTTP
- **core_mechanism:** Agents expose REST endpoints (e.g. POST /agents/{id}/runs) and exchange runs/messages as ordinary JSON over HTTP, deliberately avoiding a bespoke transport so existing web infrastructure applies.
- **discovery_endpoint:** REST agent endpoints (implementation-defined; e.g. /agents/{id})
- **settlement_type:** —
- **adoption_metric:** — (verify-against-primary-at-build)
- **notable_adopters:** {"value":"IBM","source":"https://agentcommunicationprotocol.dev"}
- **relationships:** {"predicate":"competes_with","target":"a2a","note":"ACP is positioned as a REST-native alternative to A2A for inter-agent messaging."}
- **ideal_use_case:** Teams that want agent-to-agent messaging using plain REST conventions and existing HTTP tooling.
- **when_to_use:** When you prefer a low-ceremony REST interface for agent messaging over A2A's richer agent-card + task model.
- **when_not_to_use:** When you need the broad ecosystem, Agent Cards, and governance of A2A, or cross-vendor production interop today.
- **code_example:** POST /agents/researcher/runs HTTP/1.1
Content-Type: application/json

{ "input": [{ "role": "user", "content": "Summarize the agentic web" }] }
- **source:** Spec home: https://agentcommunicationprotocol.dev . Maintainer (IBM/AGNTCY): research §2 (AGNTCY listed among protocols to add).
- **agent_readiness_link:** agent-readiness/a2a
- **layer_legacy:** agent