Agent Communication Protocol ACP
Coordinate IBM's Agent Communication Protocol (ACP) was an open REST protocol, built by IBM's BeeAI project, for exchanging multimodal messages (text, code, files, media) between agents, applications, and people, with support for synchronous, background, and streamed responses and for stateless or stateful execution [1][2]. It solved the same problem A2A now solves: letting agents built on different frameworks discover each other's capabilities (GET /agents) and run tasks (POST /runs) over a standard REST/OpenAPI surface, and it powered agent discovery and execution on IBM's BeeAI Platform [1].
Overview
ACP does not exist as an independent, live protocol any more. Its GitHub repository (i-am-bee/acp) was archived by its owner on 2025-08-27 and is now read-only [1]; the repository's README carries a banner stating "ACP is now part of A2A under the Linux Foundation!" and links a migration guide directing implementers to Google/Linux Foundation's A2A protocol instead [1]. Because the record here would otherwise duplicate a step already covered by a2a, and because the issuer itself declares the protocol subsumed, this record's phase is set to "withdrawn" and its implementation to "deprecated" per Ruling 11 — it is kept as a historical record rather than deleted, since some deployments and SDKs (acp-sdk on PyPI/npm) may still exist in the wild.
At time of archival the last published OpenAPI spec was v0.2.0, exposing GET /ping (liveness), GET /agents (agent discovery, paginated via limit/offset), and a /runs family of endpoints for execution [2]. Governance had been IBM BeeAI-led community governance; there is no evidence ACP itself was ever formally adopted by a Linux Foundation working group before being merged — rather, its functionality and some contributors moved into the A2A project, which is the Linux Foundation-governed successor. What is unresolved: whether any production deployments continue to run the archived ACP server surface independently of A2A; no such deployment was found during this verification pass.
Discovery and probe
GET /agents (Agent Discovery endpoint) · /agents
GET {origin}/agents
parse: JSON array of agent objects would confirm a live ACP server; in practice the repository is archived and this is not expected to resolve on new deployments
on absent: Expected: the protocol was retired in August 2025 and superseded by A2A, so absence is the normal case
History
- 2026-09-05 — seeded from Exa Agent research run
- 2026-09-06 — verified against github.com/i-am-bee/acp (archived banner, archive date) and its OpenAPI spec; set phase withdrawn per Ruling 11 as merged into A2A
- 2026-09-06 — collisions updated to add Agent Connect Protocol (Cisco/AGNTCY), verified against github.com/agntcy/acp-spec, spec.acp.agntcy.org
Instances
- IBM BeeAI Platform (historical, prior to migration to A2A) · Observed 2026-09-05 · service
- i-am-bee/acp (archived reference server) · Observed 2026-09-05 · service
See also
- Agent Client Protocol
- Agentic Commerce Protocol
- Agent Connect Protocol (AGNTCY)
- ACP (three protocols)
- Not to be confused with: Agent Client Protocol (Zed), Agentic Commerce Protocol (OpenAI/Stripe), Agent Connect Protocol (AGNTCY)
References
- The i-am-bee/acp GitHub repository was archived by the owner on 2025-08-27 and is read-only; its README banner states "ACP is now part of A2A under the Linux Foundation!" with a link to a migration guide. — https://github.com/i-am-bee/acp (2026-09-05) VERIFIED
- The ACP OpenAPI specification (v0.2.0) defines GET /agents for agent discovery, GET /ping for liveness, and a /runs resource for stateless/stateful/streamed execution. — https://raw.githubusercontent.com/i-am-bee/acp/main/docs/spec/openapi.yaml (2026-09-05) VERIFIED