Agent Commerce Kit (ACK) vs Agent Payments Protocol (AP2)
The map lists them as complementary: sites and agents commonly implement both.
| Agent Commerce Kit (ACK) ACK | Agent Payments Protocol AP2 | |
|---|---|---|
| Lifecycle step | 7 Pay: Settle the bill | 7 Pay: Settle the bill |
| Answers | How can an agent prove who owns it and pay another party, on any rail, with a receipt both sides can verify? | Did the user actually authorize what this agent is about to buy and pay for, and can the merchant prove it later? |
| Governed by | Developed by Catena Labs and contributed as MIT-licensed open source (agentcommercekit/ack); no standards body | Google; core specification donated to the FIDO Alliance (Payments TWG and Agentic Authentication TWG), 2026-04-28; the google-agentic-commerce/AP2 repository now hosts only samples and an SDK, not the normative spec text |
| Status (issuer's words) | Open protocols with no stated version, status or date on the concepts page; reference packages tagged up to agentcommercekit@0.11.0 | Security/authorization protocol for agent-performed payments; core spec now stewarded by FIDO Alliance |
| Version | unversioned docs; reference packages agentcommercekit@0.11.0 (2026-10-16) | v0.2.0 (2026-04-28) |
| Form / transport | document format | endpoint |
| Found at | none at a fixed path; identity rests on DIDs and verifiable credentials exchanged between the parties | none |
| Implementation | prototype | multi-implementation — Google (launch blog post, 60+ launch partners) |
| Evidence | 2 verified, 1 reported | 4 verified, 2 reported |
| Primary use case | Accept payments from agents | Let agents buy on behalf of a person |
| Last verified | 2026-10-23 (current) | 2026-10-23 (current) |
| Specification | https://www.agentcommercekit.com/overview/concepts | https://raw.githubusercontent.com/google-agentic-commerce/AP2/main/docs/ap2/specification.md |
When to use which
- Choose Agent Commerce Kit (ACK) when your question is “How can an agent prove who owns it and pay another party, on any rail, with a receipt both sides can verify?” and you accept its maturity: status "Open protocols with no stated version, status or date on the concepts page; reference packages tagged up to agentcommercekit@0.11.0", implementation prototype.
- Choose Agent Payments Protocol when your question is “Did the user actually authorize what this agent is about to buy and pay for, and can the merchant prove it later?” and you accept its maturity: status "Security/authorization protocol for agent-performed payments; core spec now stewarded by FIDO Alliance", implementation multi-implementation (Google (launch blog post, 60+ launch partners)).
Read the full articles
- Agent Commerce Kit (ACK): How can an agent prove who owns it and pay another party, on any rail, with a receipt both sides can verify?
- Agent Payments Protocol: Did the user actually authorize what this agent is about to buy and pay for, and can the merchant prove it later?