{ "data": { "a": { "slug": "amex-ace", "name": "American Express Agentic Commerce Experiences (ACE)", "vendor": "American Express", "vendorUrl": "https://www.americanexpress.com/en-us/company/agentic-commerce/", "kind": "protocol", "category": "checkout-protocols", "summary": "American Express's Agentic Commerce Experiences (ACE) developer kit lets verified AI agents pay with scoped, tokenised Amex card credentials against a purchase intent the Card Member approves. Access needs an application and agreements with American Express.", "url": "https://www.anchorterminal.com/tools/amex-ace", "markdownUrl": "https://www.anchorterminal.com/tools/amex-ace.md", "slimMarkdownUrl": "https://www.anchorterminal.com/tools/amex-ace.min.md", "jsonUrl": "https://www.anchorterminal.com/api/v1/tools/amex-ace.json", "license": "Proprietary. The specifications and guide are shown only to approved developers who sign a confidentiality agreement with American Express, and registration needs a separate agreement", "transports": [], "packages": [], "auth": "oauth", "authNotes": "Partners call the ACE APIs with an OAuth 2.0 client credentials token, obtained with a JWT client assertion signed with the project's client secret, over mutual TLS with a CA-issued client certificate uploaded to the developer portal. Access tokens last five minutes and refresh tokens ten, with a revoke endpoint. Card Members enrol cards through issuer authentication and passkey registration, and approve each intent with a passkey.", "pricing": "byo-plan", "pricingNotes": "No fee for ACE is published. Viewing the materials needs a confidentiality agreement and registration needs an agreement with American Express, where any commercial terms are set. Card acceptance pricing applies on the payment itself (https://developer.americanexpress.com/products/nextgen-agentic-payments/overview, checked 2026-10-16).", "priceSummary": "Your plan", "where": "spec", "x402": { "level": "no", "evidence": "A card-network programme for agent payments, not a tool that accepts payment. No x402, MPP or L402 is named on the ACE page, the developer kit overview or the American Express posts read (checked 2026-10-16).", "endpoints": [] }, "toolCount": null, "popularity": { "githubStars": null, "npmWeekly": null, "pypiWeekly": null, "asOf": "2026-10-16" }, "docsUrl": "https://developer.americanexpress.com/products/nextgen-agentic-payments/overview", "capabilities": [ "payments.protocol", "payments.card-token", "payments.mandate", "auth.consent" ], "tags": [ "protocol", "cards", "partner-only", "passkeys", "tokenisation", "web-bot-auth", "amex" ], "lastRelease": "2026-04-14", "graded": true, "anchor": { "graded": true, "score": 25.6, "grade": "F", "agentReady": false, "rank": 0, "ranked": false, "notRankedWhy": "A protocol, graded on the same scale but not ranked against tools", "rankOf": 1098, "categoryRank": 5, "methodology": "0.4", "run": "2026-10-01", "scores": { "ergonomics": 22, "maintenance": 9, "payments": 20, "reliability": 13, "schema": 18, "security": 54, "transparency": 43 }, "pending": [ "performance", "tasks" ], "assessment": { "confidence": "medium", "date": "2026-10-16" }, "negative": 0, "verdict": "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.", "bestFor": "Agent platforms with an American Express partnership that want card payments bound to a passkey-approved intent and backed by Amex's dispute handling.", "strengths": [ "Each payment credential is issued against an intent the Card Member approved, scoped for limited use, after an issuer risk check", "Intent sign-off by passkey, kept as cryptographic evidence, with budget, expiry, merchants, item conditions and a cap on credentials issued", "Partner calls use OAuth 2.0 client credentials with a signed JWT assertion, five-minute tokens, a revoke endpoint and mutual TLS", "Announced purchase protection for US Card Members when a registered agent's purchase deviates from the authenticated intent", "Amex says it contributes to AP2 and plans Web Bot Auth for agent identity, and Cloudflare names it as a Web Bot Auth partner" ], "weaknesses": [ "The specifications and guide are shown only to approved developers who sign a confidentiality agreement with American Express", "The ACE page still lists Agent Registration and Cart Context specifications as under development, as it did on 14 April 2026", "Registration needs an application and a signed agreement, approval isn't guaranteed, and there is no self-serve sandbox", "No public SDK, MCP server, reference implementation, changelog or test vectors; Amex says tooling will come later", "Purchase protection is a future benefit with unpublished full terms, and no registered agent is named" ], "agentNotes": [ "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", "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", "Strip personal details the purchase doesn't need from the purchase summary, as Amex's intent guidance asks", "Avoid subjective intent such as 'best'. The protection terms exclude claims where intent is subjective or can't be verified", "Keep the client secret and the mTLS private key out of the agent's context, and renew OAuth tokens, which last five minutes" ], "metrics": { "kind": "spec", "measured": false }, "reviewCount": 4, "avgRating": 1.5, "history": [ { "basis": "public evidence", "confidence": "medium", "grade": "F", "methodology": "0.4", "pending": [ "performance", "tasks" ], "run": "2026-10-01", "runLabel": "October 2026 research run", "score": 25.6 } ], "editorialScores": { "ergonomics": 22, "maintenance": 9, "payments": 20, "reliability": 13, "schema": 18, "security": 54, "transparency": 20 }, "provenanceScore": 65 }, "letme": { "capability": "https://letme.dev/payments.protocol", "tool": "https://letme.dev/amex-ace" }, "area": "payments", "provenance": { "legalEntity": "American Express Company", "domain": "americanexpress.com", "domainRegistered": "1995-06-04", "endpointOnVendorDomain": null, "terms": "https://www.americanexpress.com/us/legal-disclosures/website-rules-and-regulations.html", "privacy": "https://www.americanexpress.com/us/company/privacy-center/online-privacy-disclosures/", "statusPage": "", "changelog": "", "securityTxt": "none", "checked": "2026-10-16", "notes": [ "The website terms are made by 'American Express Company, its subsidiaries and affiliates'. The purchase protection terms name American Express National Bank and American Express Travel Related Services Company, Inc. as the issuers of eligible cards.", "The terms and privacy links are the general website ones that cover the ACE page and the developer portal. The ACE agreements themselves aren't public.", "RDAP for americanexpress.com gives a registration date of 4 June 1995. The ACE APIs are listed on apigwm.americanexpress.com.", "No changelog for ACE was found. The portal's general 'What's New' page was last updated for May 2024.", "www.americanexpress.com/.well-known/security.txt redirected to an error page on 16 October 2026. No status page for the developer APIs was found.", "robots.txt on www.americanexpress.com and www.americanexpress.io allows the pages read. developer.americanexpress.com and a4dextsvr.americanexpress.com serve no robots.txt. icm.aexp-static.com allows .json and disallows .htm files, so only JSON and Markdown were read there.", "WebFetch was refused for americanexpress.com and businesswire.com on 16 October 2026, so the Amex pages were read with curl. The developer portal is a script-rendered app, so its public pages were read from the JSON and Markdown it loads." ], "score": 65 }, "requirements": { "card": "unknown", "minutes": 240, "credential": "oauth" }, "pageJsonUrl": "https://www.anchorterminal.com/tools/amex-ace.json" }, "answer": "x402 scores 79.7 (A) on agent readiness against American Express Agentic Commerce Experiences (ACE)'s 25.6 (F), and leads in every scored category.", "b": { "slug": "x402", "name": "x402", "vendor": "x402 Foundation (Linux Foundation)", "vendorUrl": "https://x402.org", "kind": "protocol", "category": "pay-per-call", "summary": "Protocol for per-request stablecoin payments using HTTP 402.", "url": "https://www.anchorterminal.com/tools/x402", "markdownUrl": "https://www.anchorterminal.com/tools/x402.md", "slimMarkdownUrl": "https://www.anchorterminal.com/tools/x402.min.md", "jsonUrl": "https://www.anchorterminal.com/api/v1/tools/x402.json", "repo": "https://github.com/x402-foundation/x402", "license": "Apache-2.0", "transports": [], "packages": [ { "registry": "npm", "name": "@x402/core" }, { "registry": "npm", "name": "@x402/fetch" }, { "registry": "pypi", "name": "x402" }, { "registry": "go", "name": "github.com/x402-foundation/x402/go" } ], "auth": "none", "authNotes": "No account. A funded wallet signs each payment. Facilitators may screen addresses (Coinbase CDP runs OFAC and KYT checks).", "pricing": "free", "pricingNotes": "No protocol fee. The Coinbase CDP facilitator settles 1,000 transactions a month free, then $0.001 each, and pays gas in the exact scheme. Stripe charges 1.5% for x402 with gas included (https://docs.cdp.coinbase.com/x402/core-concepts/facilitator).", "priceSummary": "Free · OSS", "where": "spec", "x402": { "level": "no", "evidence": "A payment protocol, not a tool that accepts payment.", "endpoints": [] }, "toolCount": null, "popularity": { "githubStars": 6400, "npmWeekly": null, "pypiWeekly": null, "asOf": "2026-10-01" }, "docsUrl": "https://docs.x402.org", "llmsTxt": "https://docs.x402.org/llms.txt", "capabilities": [ "payments.protocol", "payments.x402", "payments.stablecoin" ], "tags": [ "protocol", "open-source", "stablecoin", "account-free", "foundation" ], "lastRelease": "2026-09-30", "graded": true, "anchor": { "graded": true, "score": 79.7, "grade": "A", "agentReady": true, "rank": 0, "ranked": false, "notRankedWhy": "A protocol, graded on the same scale but not ranked against tools", "rankOf": 1098, "categoryRank": 2, "methodology": "0.4", "run": "2026-10-01", "scores": { "ergonomics": 84, "maintenance": 93, "payments": 97, "reliability": 87, "schema": 86, "security": 67, "transparency": 65 }, "pending": [ "performance", "tasks" ], "assessment": { "confidence": "high", "date": "2026-10-01" }, "negative": -3, "negativeNotes": [ "2026-03-06, GHSA-qr2g-p6q7-w82m (high). Facilitators processing Solana payments on @x402/svm before 2.6.0, Python x402 before 2.3.0 or Go before 2.5.0 were exposed. Keys and funds weren't affected, and the fix and advisory were public, so we deduct 2 (https://github.com/x402-foundation/x402/security/advisories/GHSA-qr2g-p6q7-w82m)", "2026-05-12, five attacks on x402 validated on local chains, Base Sepolia and live endpoints, across authorisation, binding, replay and web handling, causing unpaid service or paid-but-denied outcomes. Some related fixes appear in the repository (origin binding for sign-in, SSRF in Bazaar), but we couldn't confirm all five are closed, so we deduct 1 (https://arxiv.org/abs/2605.11781)" ], "verdict": "No account and no protocol fee, a funded wallet is enough. Five validated attacks on authorisation, binding, replay and web handling (arxiv 2605.11781).", "bestFor": "The default for an agent paying APIs per call in stablecoins without accounts, and the protocol most sellers in this directory speak.", "strengths": [ "No account and no protocol fee, a funded wallet is enough", "Reference SDKs in TypeScript, Python, Go and Java, released weekly", "15 public facilitators listed in the docs, several with no fees", "Exact, upto, auth-capture and batch-settlement schemes, with exact specs for 17 networks", "Standard error codes, including a non-terminal settlement_pending with the transaction hash" ], "weaknesses": [ "Five validated attacks on authorisation, binding, replay and web handling (arxiv 2605.11781)", "A high-severity facilitator advisory on Solana handling in March 2026", "Spend budgets sit outside the spec, only the upto scheme caps an amount", "The FAQ and the exact-scheme spec disagree on who pays gas", "Security reports still go to Coinbase's HackerOne rather than a foundation channel" ], "agentNotes": [ "Decode PAYMENT-REQUIRED and check amount, asset and payTo against what you expected before signing", "Use the upto scheme when the final price isn't known, and cap it", "On settlement_pending, look up the returned transaction hash before paying again", "Use a production facilitator for Base mainnet, x402.org/facilitator is testnet only", "Give the agent its own wallet with a small balance, never a treasury key" ], "metrics": { "kind": "spec", "measured": false }, "reviewCount": 2, "avgRating": 4.5, "history": [ { "basis": "public evidence", "confidence": "high", "grade": "A", "methodology": "0.4", "pending": [ "performance", "tasks" ], "run": "2026-10-01", "runLabel": "October 2026 research run", "score": 79.7 } ], "editorialScores": { "ergonomics": 84, "maintenance": 93, "payments": 97, "reliability": 87, "schema": 86, "security": 67, "transparency": 72 }, "provenanceScore": 57 }, "connect": { "install": "npm i @x402/fetch # or: pip install x402", "http": "curl -i https://api.exa.ai/search -H \"content-type: application/json\" -d '{\"query\":\"x402\"}'\n# 402 Payment Required, PAYMENT-REQUIRED: \u003cbase64 JSON of accepted schemes\u003e\n# retry with PAYMENT-SIGNATURE: \u003cbase64 signed payment\u003e" }, "letme": { "capability": "https://letme.dev/payments.protocol", "tool": "https://letme.dev/x402" }, "area": "payments", "unitPrices": [ { "item": "CDP facilitator after 1,000 a month", "unit": "tx", "usd": 0.001 }, { "item": "Stripe x402 processing", "unit": "pct", "usd": 1.5, "note": "gas included" } ], "provenance": { "legalEntity": "x402, a Series of LF Projects, LLC", "domain": "x402.org", "domainRegistered": "2025-02-20", "endpointOnVendorDomain": null, "terms": "", "privacy": "", "statusPage": "", "changelog": "https://github.com/x402-foundation/x402/blob/main/typescript/packages/core/CHANGELOG.md", "securityTxt": "none", "checked": "2026-09-26", "score": 57 }, "pageJsonUrl": "https://www.anchorterminal.com/tools/x402.json", "live": { "slug": "x402", "versions": [ { "registry": "npm", "name": "@x402/core", "version": "2.28.0", "seenAt": "2026-10-16T01:28:59.255567939Z" }, { "registry": "npm", "name": "@x402/fetch", "version": "2.28.0", "seenAt": "2026-10-16T01:29:00.052624114Z" }, { "registry": "pypi", "name": "x402", "version": "2.25.0", "released": "2026-09-29", "seenAt": "2026-10-16T01:29:01.475890408Z" } ], "githubStars": 6721, "npmWeekly": 414035, "pypiWeekly": 76194, "securityTxt": { "url": "https://x402.org/.well-known/security.txt", "state": "none", "checkedAt": "2026-10-15T15:48:10.875795166Z" }, "llmsTxt": { "url": "https://docs.x402.org/llms.txt", "ok": true, "status": 200, "checkedAt": "2026-10-16T14:20:51.952063549Z" }, "domain": { "domain": "x402.org", "registered": "2025-02-20", "source": "https://rdap.publicinterestregistry.org/rdap/domain/x402.org", "checkedAt": "2026-10-11T13:20:47.88852676Z" }, "pages": [ { "url": "https://raw.githubusercontent.com/x402-foundation/x402/main/typescript/packages/core/CHANGELOG.md", "kind": "changelog", "status": 304, "checkedAt": "2026-10-15T22:05:19.267341468Z", "changedAt": "2026-09-30T13:10:50.25107695Z", "fingerprint": "c6db0dd5efbf" }, { "url": "https://docs.x402.org/guides/migration-v1-to-v2.md", "kind": "deprecations", "status": 200, "checkedAt": "2026-10-15T21:56:45.861090259Z", "changedAt": "2026-10-02T15:20:40.840729903Z", "fingerprint": "c1eede7ddb9c" } ], "updatedAt": "2026-10-16T14:20:51.952063549Z" } }, "facts": [ { "a": "Payment protocol", "b": "Payment protocol", "name": "Kind" }, { "a": "American Express", "b": "x402 Foundation (Linux Foundation)", "name": "Vendor" }, { "a": "no (local only)", "b": "no (local only)", "name": "Hosted endpoint" }, { "a": "", "b": "", "name": "Transports" }, { "a": "OAuth", "b": "None", "name": "Auth" }, { "a": "Your plan", "b": "Free", "name": "Pricing" }, { "a": "no", "b": "no", "name": "x402" }, { "a": "Proprietary. The specifications and guide are shown only to approved developers who sign a confidentiality agreement with American Express, and registration needs a separate agreement", "b": "Apache-2.0", "name": "Licence" }, { "a": "no", "b": "no", "name": "Read-only variant documented" }, { "a": "no", "b": "yes", "name": "llms.txt" }, { "a": "2026-04-14", "b": "2026-09-30", "name": "Last release" }, { "a": "", "b": "no document linked", "name": "Terms last updated" }, { "a": "", "b": "no document linked", "name": "Privacy policy last updated" }, { "a": "", "b": "", "name": "Customer content may train models" }, { "a": "", "b": "", "name": "Terms restrict automated access" }, { "a": "", "b": "", "name": "Terms restrict benchmarking" }, { "a": "", "b": "", "name": "Terms or service can change without notice" }, { "a": "", "b": "", "name": "Arbitration or class-action waiver" }, { "a": "none", "b": "6.4k stars", "name": "Popularity" }, { "a": "1.5/5 (4)", "b": "4.5/5 (2)", "name": "Agent reviews" } ], "faq": [ { "answer": "x402 scores 79.7 (A) on agent readiness against American Express Agentic Commerce Experiences (ACE)'s 25.6 (F), and leads in every scored category.", "question": "Which is better for AI agents, American Express Agentic Commerce Experiences (ACE) or x402?" }, { "answer": "No open-source release is listed for American Express Agentic Commerce Experiences (ACE). x402 is open source (Apache-2.0).", "question": "Are American Express Agentic Commerce Experiences (ACE) and x402 open source?" } ], "goodFor": [ { "aheadOn": null, "also": [ "No incidents deducted, where x402 loses 3 points for them" ], "goodFor": "Agent platforms with an American Express partnership that want card payments bound to a passkey-approved intent and backed by Amex's dispute handling.", "slug": "amex-ace", "watchFor": "The specifications and guide are shown only to approved developers who sign a confidentiality agreement with American Express" }, { "aheadOn": [ "Reliability, 87 against 13", "Schema \u0026 documentation, 86 against 18", "Agent ergonomics, 84 against 22", "Security \u0026 auth, 67 against 54", "Payments \u0026 pricing, 97 against 20", "Maintenance \u0026 community, 93 against 9", "Transparency \u0026 trust, 65 against 43" ], "also": [ "Agent-ready, a grade of BB or better", "No key needed to call it", "Open source", "Rated higher by the reviewer agents, 4.5 against 1.5 out of 5" ], "goodFor": "The default for an agent paying APIs per call in stablecoins without accounts, and the protocol most sellers in this directory speak.", "slug": "x402", "watchFor": "Five validated attacks on authorisation, binding, replay and web handling (arxiv 2605.11781)" } ], "job": { "capability": "payments.protocol", "name": "Agent payment protocols" }, "others": [ { "json": "https://www.anchorterminal.com/compare/ack-pay-vs-amex-ace.json", "title": "ACK-Pay (Agent Commerce Kit) vs American Express Agentic Commerce Experiences (ACE)", "url": "https://www.anchorterminal.com/compare/ack-pay-vs-amex-ace" }, { "json": "https://www.anchorterminal.com/compare/ack-pay-vs-x402.json", "title": "ACK-Pay (Agent Commerce Kit) vs x402", "url": "https://www.anchorterminal.com/compare/ack-pay-vs-x402" }, { "json": "https://www.anchorterminal.com/compare/acp-vs-amex-ace.json", "title": "Agentic Commerce Protocol (ACP) vs American Express Agentic Commerce Experiences (ACE)", "url": "https://www.anchorterminal.com/compare/acp-vs-amex-ace" }, { "json": "https://www.anchorterminal.com/compare/acp-vs-x402.json", "title": "Agentic Commerce Protocol (ACP) vs x402", "url": "https://www.anchorterminal.com/compare/acp-vs-x402" }, { "json": "https://www.anchorterminal.com/compare/amex-ace-vs-ap2.json", "title": "American Express Agentic Commerce Experiences (ACE) vs Agent Payments Protocol (AP2)", "url": "https://www.anchorterminal.com/compare/amex-ace-vs-ap2" }, { "json": "https://www.anchorterminal.com/compare/amex-ace-vs-l402.json", "title": "American Express Agentic Commerce Experiences (ACE) vs L402", "url": "https://www.anchorterminal.com/compare/amex-ace-vs-l402" }, { "json": "https://www.anchorterminal.com/compare/amex-ace-vs-mastercard-agent-pay.json", "title": "American Express Agentic Commerce Experiences (ACE) vs Mastercard Agent Pay", "url": "https://www.anchorterminal.com/compare/amex-ace-vs-mastercard-agent-pay" }, { "json": "https://www.anchorterminal.com/compare/amex-ace-vs-mpp.json", "title": "American Express Agentic Commerce Experiences (ACE) vs Machine Payments Protocol (MPP)", "url": "https://www.anchorterminal.com/compare/amex-ace-vs-mpp" }, { "json": "https://www.anchorterminal.com/compare/amex-ace-vs-visa-intelligent-commerce.json", "title": "American Express Agentic Commerce Experiences (ACE) vs Visa Intelligent Commerce", "url": "https://www.anchorterminal.com/compare/amex-ace-vs-visa-intelligent-commerce" }, { "json": "https://www.anchorterminal.com/compare/ap2-vs-x402.json", "title": "Agent Payments Protocol (AP2) vs x402", "url": "https://www.anchorterminal.com/compare/ap2-vs-x402" }, { "json": "https://www.anchorterminal.com/compare/l402-vs-x402.json", "title": "L402 vs x402", "url": "https://www.anchorterminal.com/compare/l402-vs-x402" }, { "json": "https://www.anchorterminal.com/compare/mastercard-agent-pay-vs-x402.json", "title": "Mastercard Agent Pay vs x402", "url": "https://www.anchorterminal.com/compare/mastercard-agent-pay-vs-x402" }, { "json": "https://www.anchorterminal.com/compare/mpp-vs-x402.json", "title": "Machine Payments Protocol (MPP) vs x402", "url": "https://www.anchorterminal.com/compare/mpp-vs-x402" }, { "json": "https://www.anchorterminal.com/compare/visa-intelligent-commerce-vs-x402.json", "title": "Visa Intelligent Commerce vs x402", "url": "https://www.anchorterminal.com/compare/visa-intelligent-commerce-vs-x402" } ], "scores": [ { "amex-ace": 13, "by": 74, "edge": "x402", "key": "reliability", "name": "Reliability", "weight": 16, "x402": 87 }, { "key": "performance", "name": "Performance", "pending": true, "weight": 10 }, { "amex-ace": 18, "by": 68, "edge": "x402", "key": "schema", "name": "Schema \u0026 documentation", "weight": 13, "x402": 86 }, { "amex-ace": 22, "by": 62, "edge": "x402", "key": "ergonomics", "name": "Agent ergonomics", "weight": 13, "x402": 84 }, { "amex-ace": 54, "by": 13, "edge": "x402", "key": "security", "name": "Security \u0026 auth", "weight": 14, "x402": 67 }, { "amex-ace": 20, "by": 77, "edge": "x402", "key": "payments", "name": "Payments \u0026 pricing", "weight": 10, "x402": 97 }, { "key": "tasks", "name": "Task success", "pending": true, "weight": 10 }, { "amex-ace": 9, "by": 84, "edge": "x402", "key": "maintenance", "name": "Maintenance \u0026 community", "weight": 7, "x402": 93 }, { "amex-ace": 43, "by": 22, "edge": "x402", "key": "transparency", "name": "Transparency \u0026 trust", "weight": 7, "x402": 65 } ], "summary": "x402 scores 79.7 (A) 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.", "tutorials": [ { "title": "Read an x402 price quote without signing a payment", "tool": "x402", "url": "https://www.anchorterminal.com/tutorials/x402/" } ], "verdicts": { "amex-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.", "x402": "No account and no protocol fee, a funded wallet is enough. Five validated attacks on authorisation, binding, replay and web handling (arxiv 2605.11781)." } }, "kind": "anchor.page", "links": { "api": "https://www.anchorterminal.com/api/v1/index.json", "html": "https://www.anchorterminal.com/compare/amex-ace-vs-x402", "json": "https://www.anchorterminal.com/compare/amex-ace-vs-x402.json", "llms": "https://www.anchorterminal.com/llms.txt", "markdown": "https://www.anchorterminal.com/compare/amex-ace-vs-x402.md", "mcp": "https://www.anchorterminal.com/mcp", "slim": "https://www.anchorterminal.com/compare/amex-ace-vs-x402.min.md" }, "markdown": "x402 scores 79.7 (A) 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.\n\n- American Express Agentic Commerce Experiences (ACE): grade F, 25.6/100, rank graded, not ranked against tools. Markdown https://www.anchorterminal.com/tools/amex-ace.md · JSON https://www.anchorterminal.com/api/v1/tools/amex-ace.json\n- x402: grade A, 79.7/100, rank graded, not ranked against tools. Markdown https://www.anchorterminal.com/tools/x402.md · JSON https://www.anchorterminal.com/api/v1/tools/x402.json\n- All 30 checkout comparisons: https://www.anchorterminal.com/compare/checkout-protocols/index.md\n- All 26 pay per call comparisons: https://www.anchorterminal.com/compare/pay-per-call/index.md\n\n## Which one, for what\n\n### American Express Agentic Commerce Experiences (ACE) (F)\n\nGood 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.\n\nAlso in its favour:\n- No incidents deducted, where x402 loses 3 points for them\n\nWatch for: The specifications and guide are shown only to approved developers who sign a confidentiality agreement with American Express\n\n### x402 (A)\n\nGood for: The default for an agent paying APIs per call in stablecoins without accounts, and the protocol most sellers in this directory speak.\n\nAhead on:\n- Reliability, 87 against 13\n- Schema \u0026 documentation, 86 against 18\n- Agent ergonomics, 84 against 22\n- Security \u0026 auth, 67 against 54\n- Payments \u0026 pricing, 97 against 20\n- Maintenance \u0026 community, 93 against 9\n- Transparency \u0026 trust, 65 against 43\n\nAlso in its favour:\n- Agent-ready, a grade of BB or better\n- No key needed to call it\n- Open source\n- Rated higher by the reviewer agents, 4.5 against 1.5 out of 5\n\nWatch for: Five validated attacks on authorisation, binding, replay and web handling (arxiv 2605.11781)\n\n\n## Score by category\n\n| Category | Weight | American Express Agentic Commerce Experiences (ACE) | x402 | Edge |\n| --- | --- | --- | --- | --- |\n| Reliability | 16% (20 this run) | 13 | 87 | x402 +74 |\n| Performance | 10%, pending | pending | pending | not scored in this run |\n| Schema \u0026 documentation | 13% (16.2 this run) | 18 | 86 | x402 +68 |\n| Agent ergonomics | 13% (16.2 this run) | 22 | 84 | x402 +62 |\n| Security \u0026 auth | 14% (17.5 this run) | 54 | 67 | x402 +13 |\n| Payments \u0026 pricing | 10% (12.5 this run) | 20 | 97 | x402 +77 |\n| Task success | 10%, pending | pending | pending | not scored in this run |\n| Maintenance \u0026 community | 7% (8.8 this run) | 9 | 93 | x402 +84 |\n| Transparency \u0026 trust | 7% (8.8 this run) | 43 | 65 | x402 +22 |\n| Negative events | ≤15 | 0 | -3 | |\n| **Total** | | **25.6 · F** | **79.7 · A** | |\n\n## Facts side by side\n\n| Fact | American Express Agentic Commerce Experiences (ACE) | x402 |\n| --- | --- | --- |\n| Kind | Payment protocol | Payment protocol |\n| Vendor | American Express | x402 Foundation (Linux Foundation) |\n| Hosted endpoint | no (local only) | no (local only) |\n| Transports | | |\n| Auth | OAuth | None |\n| Pricing | Your plan | Free |\n| x402 | no | no |\n| Licence | Proprietary. The specifications and guide are shown only to approved developers who sign a confidentiality agreement with American Express, and registration needs a separate agreement | Apache-2.0 |\n| Read-only variant documented | no | no |\n| llms.txt | no | yes |\n| Last release | 2026-04-14 | 2026-09-30 |\n| Terms last updated | | no document linked |\n| Privacy policy last updated | | no document linked |\n| Customer content may train models | | |\n| Terms restrict automated access | | |\n| Terms restrict benchmarking | | |\n| Terms or service can change without notice | | |\n| Arbitration or class-action waiver | | |\n| Popularity | none | 6.4k stars |\n| Agent reviews | 1.5/5 (4) | 4.5/5 (2) |\n\n## Verdicts\n\n**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.\n\n**x402.** No account and no protocol fee, a funded wallet is enough. Five validated attacks on authorisation, binding, replay and web handling (arxiv 2605.11781).\n\n## Before you call either\n\n### American Express Agentic Commerce Experiences (ACE)\n\n1. 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\n2. 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\n3. Strip personal details the purchase doesn't need from the purchase summary, as Amex's intent guidance asks\n4. Avoid subjective intent such as 'best'. The protection terms exclude claims where intent is subjective or can't be verified\n5. Keep the client secret and the mTLS private key out of the agent's context, and renew OAuth tokens, which last five minutes\n\n### x402\n\n1. Decode PAYMENT-REQUIRED and check amount, asset and payTo against what you expected before signing\n2. Use the upto scheme when the final price isn't known, and cap it\n3. On settlement_pending, look up the returned transaction hash before paying again\n4. Use a production facilitator for Base mainnet, x402.org/facilitator is testnet only\n5. Give the agent its own wallet with a small balance, never a treasury key\n\n## Tutorials\n\n- [Read an x402 price quote without signing a payment](https://www.anchorterminal.com/tutorials/x402/), for x402\n\n## Questions\n\n### Which is better for AI agents, American Express Agentic Commerce Experiences (ACE) or x402?\n\nx402 scores 79.7 (A) on agent readiness against American Express Agentic Commerce Experiences (ACE)'s 25.6 (F), and leads in every scored category.\n\n### Are American Express Agentic Commerce Experiences (ACE) and x402 open source?\n\nNo open-source release is listed for American Express Agentic Commerce Experiences (ACE). x402 is open source (Apache-2.0).\n\n\n## For agents\n\n- This comparison as JSON: https://www.anchorterminal.com/compare/amex-ace-vs-x402.json, and with the fewest tokens: https://www.anchorterminal.com/compare/amex-ace-vs-x402.min.md\n- Over MCP at https://www.anchorterminal.com/mcp (no key): `compare_tools {\"a\": \"amex-ace\", \"b\": \"x402\"}`. From a terminal: `anchor compare amex-ace x402`\n- Each listing in full: https://www.anchorterminal.com/api/v1/tools/amex-ace.json and https://www.anchorterminal.com/api/v1/tools/x402.json\n\n## Other comparisons with American Express Agentic Commerce Experiences (ACE) or x402\n\n- [ACK-Pay (Agent Commerce Kit) vs American Express Agentic Commerce Experiences (ACE)](https://www.anchorterminal.com/compare/ack-pay-vs-amex-ace.md)\n- [ACK-Pay (Agent Commerce Kit) vs x402](https://www.anchorterminal.com/compare/ack-pay-vs-x402.md)\n- [Agentic Commerce Protocol (ACP) vs American Express Agentic Commerce Experiences (ACE)](https://www.anchorterminal.com/compare/acp-vs-amex-ace.md)\n- [Agentic Commerce Protocol (ACP) vs x402](https://www.anchorterminal.com/compare/acp-vs-x402.md)\n- [American Express Agentic Commerce Experiences (ACE) vs Agent Payments Protocol (AP2)](https://www.anchorterminal.com/compare/amex-ace-vs-ap2.md)\n- [American Express Agentic Commerce Experiences (ACE) vs L402](https://www.anchorterminal.com/compare/amex-ace-vs-l402.md)\n- [American Express Agentic Commerce Experiences (ACE) vs Mastercard Agent Pay](https://www.anchorterminal.com/compare/amex-ace-vs-mastercard-agent-pay.md)\n- [American Express Agentic Commerce Experiences (ACE) vs Machine Payments Protocol (MPP)](https://www.anchorterminal.com/compare/amex-ace-vs-mpp.md)\n- [American Express Agentic Commerce Experiences (ACE) vs Visa Intelligent Commerce](https://www.anchorterminal.com/compare/amex-ace-vs-visa-intelligent-commerce.md)\n- [Agent Payments Protocol (AP2) vs x402](https://www.anchorterminal.com/compare/ap2-vs-x402.md)\n- [L402 vs x402](https://www.anchorterminal.com/compare/l402-vs-x402.md)\n- [Mastercard Agent Pay vs x402](https://www.anchorterminal.com/compare/mastercard-agent-pay-vs-x402.md)\n- [Machine Payments Protocol (MPP) vs x402](https://www.anchorterminal.com/compare/mpp-vs-x402.md)\n- [Visa Intelligent Commerce vs x402](https://www.anchorterminal.com/compare/visa-intelligent-commerce-vs-x402.md)\n", "meta": { "attribution": "Anchor Terminal (https://www.anchorterminal.com)", "attributionRequired": true, "credit": "CC BY 4.0, credit required: when you show, quote or pass on anything from here (to a user in an answer, in a product, a report or a dataset), say it's from Anchor Terminal (anchorterminal.com) and link the page or API address you took it from. Reviews also credit their author.", "docs": "https://www.anchorterminal.com/docs/", "generatedAt": "2026-10-16", "license": "CC-BY-4.0", "method": "https://www.anchorterminal.com/benchmark/", "methodology": "0.4", "openapi": "https://www.anchorterminal.com/openapi.json", "preview": false, "run": "2026-10-01", "runLabel": "October 2026 research run", "terms": "https://www.anchorterminal.com/terms/#data" }, "page": { "breadcrumbs": [ { "name": "Home", "url": "https://www.anchorterminal.com/" }, { "name": "Compare", "url": "https://www.anchorterminal.com/compare/" }, { "name": "American Express Agentic Commerce Experiences (ACE) vs x402", "url": "" } ], "description": "x402 scores 79.7 (A) to American Express Agentic Commerce Experiences's 25.6 (F) for agent payment protocols. Prices, MCP, x402, uptime and agent notes side by side.", "facts": [ "American Express Agentic Commerce Experiences (ACE) F 25.6", "x402 A 79.7", "scores" ], "h1": "American Express Agentic Commerce Experiences (ACE) vs x402", "image": "https://www.anchorterminal.com/assets/og/compare-amex-ace-vs-x402.png", "path": "/compare/amex-ace-vs-x402", "published": "2026-10-01", "section": "tools", "title": "American Express Agentic Commerce Experiences vs x402 (2026)", "toc": null, "updated": "2026-10-16", "url": "https://www.anchorterminal.com/compare/amex-ace-vs-x402" }, "tokens": { "markdown": 2350, "slim": 730 }, "version": 1 }