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Agent Connect Protocol (AGNTCY) ACP

Act The Agent Connect Protocol (ACP), published by the AGNTCY Collective (co-founded by Cisco and LangChain), defines a standard REST/OpenAPI interface for invoking and configuring a remote agent over an API — covering agent discovery/search, stateless Runs, stateful Thread Runs with checkpointed state history, and streaming output [1][2]. It targets the same problem the Agent Client Protocol (Zed) and IBM's now-retired Agent Communication Protocol both address — a standard invocation surface for interchangeable agents — but is a third, independently governed specification that also happens to be commonly abbreviated "ACP," a collision the AGNTCY project shares with at least two other unrelated "ACP" specifications tracked on this map [1].

Overview

ACP does not itself define agent-to-agent negotiation or a payments layer; its scope is narrowly the client/orchestrator-to-agent invocation surface, with agent metadata for richer discovery deferred to a separate 'agent directory' concept. It also does not define transport beyond HTTP/REST — there is no WebSocket or message-queue binding in the specification.

As of this check (September 2026), the specification's source repository (agntcy/acp-spec) was archived by its owner on 2026-04-11 and is now read-only, with its last substantive commit dated 2025-05-23 [1]. The rendered interactive OpenAPI documentation at spec.acp.agntcy.org still resolves and is served unchanged since that date, so existing implementations can still consult it, but no further spec development is occurring under this repository [2]. The broader AGNTCY Collective remains highly active — 49 public repositories with commits as recent as hours before this check — but its current discovery and identity work is concentrated in newer projects ('dir', a distributed agent directory, and 'oasf', the Open Agentic Schema Framework) rather than in acp-spec, suggesting AGNTCY's own architecture has moved on from this component without a formal deprecation notice or migration guide comparable to IBM's ACP-to-A2A banner [3].

Governance was, and nominally remains, the AGNTCY Collective's open, multi-vendor structure (Apache 2.0 license, public GitHub PR process, 'Copyright AGNTCY Contributors'). What is unresolved: whether any production deployments still run ACP servers independently of the newer 'dir'-based tooling, and whether AGNTCY intends to formally retire or fold ACP's invocation surface into a successor — no such announcement was found during this verification pass, only the archival action itself.

Discovery and probe

An agent's ACP capabilities are described in an 'ACP descriptor' retrievable via the ACP interface itself or embedded in that agent's record in an AGNTCY agent directory (now superseded in AGNTCY's active tooling by the 'dir' project); no site-wide well-known path is defined · /agents/search

POST {origin}/agents/search
parse:     A 200 response returning a JSON array of agent objects (each with agent_id and metadata.ref) confirms an ACP-speaking server per the v0.2.3 OpenAPI schema.
on absent: A 404 or non-JSON response means no ACP server at this origin. Because the specification's own source repository was archived by its owner in April 2026 with no announced successor, absence is the expected and increasingly common result over time.

Not probed live: unsafe-post. The probe is POST /agents/search.

History

Instances

No instances recorded yet.

See also

References

  1. The agntcy/acp-spec GitHub repository ('Agent Connect Protocol Specification', Apache-2.0, 168 stars) was archived by the owner on 2026-04-11 and is now read-only; its last commit was 2025-05-23 (PR #46, adding basic type support for input/output/config). — https://github.com/agntcy/acp-spec (2026-09-06) VERIFIED
  2. The rendered OpenAPI spec at spec.acp.agntcy.org (v0.2.3, OpenAPI 3.1.1) defines the Agents, Threads, Thread Runs, and Stateless Runs operation groups (POST /agents/search, GET/POST /threads, POST /runs, etc.) for invoking and configuring remote agents. — https://spec.acp.agntcy.org/ (2026-09-06) VERIFIED
  3. The AGNTCY GitHub organization currently lists 49 public repositories with activity within hours to days of this check, with its identity/discovery focus now centered on the 'dir' (Distributed Announce and Discovery of Multi-Agentic-Systems) and 'oasf' (Open Agentic Schema Framework) projects rather than acp-spec. — https://github.com/orgs/agntcy/repositories (2026-09-06) VERIFIED

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