ACP (Agent Communication Protocol) — superseded
A REST-based agent messaging protocol launched by IBM Research in March 2025 to power the BeeAI platform, donated to the Linux Foundation, and merged into A2A in 2025. The ACP team wound down active development and contributed its technology directly into A2A; BeeAI, the platform ACP was built for, now runs on A2A. It is no longer a standalone specification.
Why it matters for autonomous finance
Included precisely because it is superseded. Through most of 2025 there were three agent protocols in the conversation and a great deal of published comparison material assumed there still are. Anyone building an architecture against a 2025 three-protocol landscape is building against a landscape that no longer exists, and documenting the consolidation is more useful than documenting the protocol. ACP's better ideas — REST simplicity, lightweight messaging — survive inside A2A.
What it does not cover
Do not build against ACP as a peer to A2A. Existing BeeAI deployments continue to work and the reference implementation remains available, but for anything new there is one agent-to-agent standard worth targeting and it is A2A. Comparison articles dated 2025 that present three protocols are describing a resolved situation.
Superseded. See A2A. Every entry in this register carries this section. A standard read past its scope is worse than no standard, because it produces confidence without coverage.