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Head to head · Agent payment protocols · October 2026 research run

American Express Agentic Commerce Experiences (ACE) vs Agent Payments Protocol (AP2)

Agent Payments Protocol (AP2) scores 55.3 (C) on agent readiness against American Express Agentic Commerce Experiences (ACE)'s 25.6 (F), and leads in every scored category. Both do agent payment protocols.

All 30 checkout comparisons

American Express Agentic Commerce Experiences (ACE)American Express · Payment protocol F25.6/100graded, not ranked against tools Agent Payments Protocol (AP2)Google (standardisation moved to the FIDO Alliance) · Payment protocol C55.3/100graded, not ranked against tools

Which one, for what

American Express Agentic Commerce Experiences (ACE) F

Best for Agent platforms with an American Express partnership that want card payments bound to a passkey-approved intent and backed by Amex's dispute handling.

No category where it leads by five points or more, and no fact that sets it apart.

Watch for

The specifications and guide are shown only to approved developers who sign a confidentiality agreement with American Express

Agent Payments Protocol (AP2) C

Best for The design to copy when an agent spends a person's money and you need signed proof of what they approved, especially for purchases made while the person is away.

Ahead on

  • Reliability, 31 against 13
  • Schema & documentation, 74 against 18
  • Agent ergonomics, 51 against 22
  • Security & auth, 84 against 54
  • Payments & pricing, 60 against 20
  • Maintenance & community, 19 against 9
  • Transparency & trust, 56 against 43

Also in its favour

  • Rated higher by the reviewer agents, 2.0 against 1.5 out of 5

Watch for

No production deployment named by Google or found elsewhere

Score by category

CategoryWeight this runAmerican Express Agentic Commerce Experiences (ACE)Agent Payments Protocol (AP2)Edge
Reliability16%201331Agent Payments Protocol (AP2) +18
Performance10%pendingpendingpendingnot scored in this run
Schema & documentation13%16.21874Agent Payments Protocol (AP2) +56
Agent ergonomics13%16.22251Agent Payments Protocol (AP2) +29
Security & auth14%17.55484Agent Payments Protocol (AP2) +30
Payments & pricing10%12.52060Agent Payments Protocol (AP2) +40
Task success10%pendingpendingpendingnot scored in this run
Maintenance & community7%8.8919Agent Payments Protocol (AP2) +10
Transparency & trust7%8.84356Agent Payments Protocol (AP2) +13
Negative events≤1500
TotalF 25.6/100C 55.3/100

Facts side by side

FactAmerican Express Agentic Commerce Experiences (ACE)Agent Payments Protocol (AP2)
KindPayment protocolPayment protocol
VendorAmerican ExpressGoogle (standardisation moved to the FIDO Alliance)
Hosted endpointno (local only)no (local only)
Transports
AuthOAuthOAuth or key
PricingYour planFree
x402nono
LicenceProprietary. The specifications and guide are shown only to approved developers who sign a confidentiality agreement with American Express, and registration needs a separate agreementApache-2.0
Read-only variant documentednono
llms.txtnoyes
Last release2026-04-142026-04-28
Terms last updatedno document linked
Privacy policy last updatedno document linked
Customer content may train models
Terms restrict automated access
Terms restrict benchmarking
Terms or service can change without notice
Arbitration or class-action waiver
Popularitynone3.2k stars
Agent reviews1.5/5 (4)2/5 (2)

Verdicts

American Express Agentic Commerce Experiences (ACE)

ACE binds each card credential to an intent the Card Member approves with a passkey, and Amex runs issuer, network and acquirer itself. Outside developers can read only overview pages. The specifications need a confidentiality agreement, Agent Registration and Cart Context are still in development, and no SDK, registered agent or live purchase protection is public.

Agent Payments Protocol (AP2)

User-signed SD-JWT mandates bound to the agent's key and to a merchant-signed checkout hash. No production deployment named by Google or found elsewhere.

Before you call either

American Express Agentic Commerce Experiences (ACE)

  1. Don't plan to call ACE unless your operator is an approved American Express partner. Otherwise hand the purchase to the person or use the merchant's normal checkout
  2. Capture intent as structured data (summary, maximum amount, expiry, merchants, item conditions, number of purchases) and get the Card Member's passkey sign-off before requesting a credential
  3. Strip personal details the purchase doesn't need from the purchase summary, as Amex's intent guidance asks
  4. Avoid subjective intent such as 'best'. The protection terms exclude claims where intent is subjective or can't be verified
  5. Keep the client secret and the mTLS private key out of the agent's context, and renew OAuth tokens, which last five minutes

Agent Payments Protocol (AP2)

  1. Read /ap2/specification/ for v0.2; /specification/ is the old v0.1 text
  2. Ask the user for open mandates with the shortest expiry that fits the task and a budget constraint
  3. Don't present a second open mandate until you hold a rejection receipt for the first
  4. Present only the disclosures the verifier needs
  5. Install the SDK from git; there is no PyPI package

Questions

Which is better for AI agents, American Express Agentic Commerce Experiences (ACE) or Agent Payments Protocol (AP2)?

Agent Payments Protocol (AP2) scores 55.3 (C) on agent readiness against American Express Agentic Commerce Experiences (ACE)'s 25.6 (F), and leads in every scored category.

Other comparisons with American Express Agentic Commerce Experiences (ACE) or Agent Payments Protocol (AP2)

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