Commerce protocols vs payment protocols
Which part of the purchase does each layer own?
Commerce protocols describe business interactions. Payment protocols connect value transfer with permitted resource or transaction flows. Neither category alone supplies a complete merchant operation. Keep catalog truth, checkout state, user authority, payment processing and fulfillment in separate rows of your architecture. A provider can span rows; your evidence should still be scoped to each one.
What this establishes
A practical way to inspect evidence and make the next merchant decision.
What it cannot establish
An unresolved dependency remains. Treat affected claims as provisional. Live merchant deployment, private account eligibility, purchase completion or guaranteed AI selection.
The overlap
Commerce protocols describe business interactions. Payment protocols connect value transfer with permitted resource or transaction flows. Neither category alone supplies a complete merchant operation.
The merchant decision
Keep catalog truth, checkout state, user authority, payment processing and fulfillment in separate rows of your architecture. A provider can span rows; your evidence should still be scoped to each one.
Where they overlap.
Where they complement.
Compare roles and implementation work. A shared capability does not make two systems interchangeable.
| Decision dimension | ACP | UCP | MPP | x402 |
|---|---|---|---|---|
| Layer | Commerce | Commerce | Payments | Payments |
| Role | Defines commerce interactions; OpenAI also documents structured product feed ingestion. | Connects catalog, cart, checkout and related commerce capabilities across implementations. | Lets agents negotiate and pay for service access across supported payment methods. | Connects a resource request to payment requirements and a paid retry. |
| Status | beta specification | released | active individual Internet-Draft | published specification |
| Version | 2026-04-17 · repository identifies specification as beta | 2026-08-25 | draft-httpauth-payment-01 · normative core; broader SDK/method versions separate | 2 |
| Discovery | Product feeds documented | /.well-known/ucp profile; optional catalog capability | Payment offers for services | Resource-specific payment requirements |
| Checkout | Specified; merchant deployment conditional | Commerce checkout capability | Not a retail checkout model | Outside retail checkout scope |
| Payment | Handler integration; not itself a payment network | Payment handlers; complements authorization protocols | Core role: service access | HTTP 402 payment flow |
| Authorization | Integration-specific; confirm chosen flow | Can work with AP2; capability-specific | Payment method and intent dependent | Scheme-dependent |
| Transport | HTTP APIs; released repository includes MCP work | REST, MCP and A2A bindings documented | HTTP-oriented; SDK integration | HTTP-native |
| Adoption | Public spec and partner access docs; store-level use not inferred | Google and Shopify describe scoped implementations | Team documents service integrations; not independently transacted | Public implementations; merchant deployment Unknown |
| What it does not solve | Does not guarantee ChatGPT placement or automatic merchant approval. | Does not make every declared capability live on every shopping surface. | Does not supply retail catalogs, fulfillment or a complete store checkout. | Does not describe a retail order, shipping policy or return workflow. |
| Evidence | 6 source record(s) Checked 2026-09-28 public-preview; scope-dependent | 5 source record(s) Checked 2026-09-28 live; scope-dependent | 3 source record(s) Checked 2026-09-28 draft; scope-dependent | 3 source record(s) Checked 2026-09-28 live; scope-dependent |
Unknown ≠ unsupported. Announcements and product documentation are not proof of your live integration.
Overlap and replacement risk
These entries occupy different layers. They can work together; replacing one with another may leave a commerce, communication or authorization gap. Keep your source of product truth, fulfillment responsibility and payment obligations explicit.
Go to the source.
Primary documentation records what is publicly stated. It does not independently prove outcomes or your account’s eligibility.
Claim scope: Specification version and scope
Latest stable shown as 2026-04-17; development branch is not a release.
Claim scope: Structured catalog and inventory ingestion for ChatGPT
Claim scope: Product feed access
Approved partners; file and API delivery. This is not evidence of universal checkout availability.
Claim scope: Full snapshot feed delivery
At least daily delivery recommended; not a scanner protocol endpoint.
Claim scope: Version metadata and documented changes only; not merchant adoption.
SHA-256 of retrieved source response: 6b58fb81a436890ede612af94779b0b60a127d95aa0a44b8179d20bb605ca8ea
Claim scope: Version metadata and documented changes only; not merchant adoption.
SHA-256 of retrieved source response: a427ed74696286be7804bb3a4c5dc4c9461b4862da1ed461eeb3e723b03bca9a
Claim scope: Discovery profile and commerce capabilities
Version-pinned profile discovery; declared capabilities do not prove successful transactions.
Claim scope: Commerce semantics and interoperability
Claim scope: UCP merchant integration hub and AI performance insights
US rollout; later markets are future plans. Scale/performance statements are Google claims.
Claim scope: Developer UCP and Catalog access
Self-serve developer access. Conversion metrics in the article are vendor claims, not our results.
Claim scope: Version metadata and documented changes only; not merchant adoption.
SHA-256 of retrieved source response: a554d5a172bb62d0d22abda152b99817fddd9735f434866d1c49863274dc049c
Claim scope: Agent payments for web services
Open payment-method-extensible protocol; no retail-wide adoption inferred.
Claim scope: SDK interoperability
MPP team documents x402 exact flows in mppx.
Claim scope: Version metadata and documented changes only; not merchant adoption.
SHA-256 of retrieved source response: fcb287fd83f5a74d9ebf5b06ade3849cbad9ca4581a88fc075554afc28956b69
Claim scope: HTTP payment flow
Repository says canonical development moved to x402 Foundation; Coinbase repo is a development fork.
Claim scope: Internet-native payments
Claim scope: Version metadata and documented changes only; not merchant adoption.
SHA-256 of retrieved source response: aa6dc5e8ccc7758689945fc7502674f51cd0f21f09ec886aa1dbc4cd86bc81b6