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

ACK-Pay (Agent Commerce Kit) vs Machine Payments Protocol (MPP)

Machine Payments Protocol (MPP) scores 81.1 (A) on agent readiness against ACK-Pay (Agent Commerce Kit)'s 53.6 (D), and leads in 6 of 7 scored categories. ACK-Pay (Agent Commerce Kit) leads on transparency & trust. Both do agent payment protocols.

All 14 pay per call comparisons

ACK-Pay (Agent Commerce Kit)Catena Labs, Inc. · Payment protocol D53.6/100graded, not ranked against tools Machine Payments Protocol (MPP)Tempo and Stripe · Payment protocol A81.1/100graded, not ranked against tools

Which one, for what

ACK-Pay (Agent Commerce Kit) D

Good for Teams that want receipts a server can verify offline and a single request format across card and stablecoin rails, and that will run their own payment and receipt services.

Ahead on

  • Transparency & trust, 60 against 45

Watch for

No public Payment Service or Receipt Service was found. The docs use example.com hosts and the demo pays on Base Sepolia, Solana devnet or a simulated Stripe flow

Machine Payments Protocol (MPP) A

Good for Sellers who want stablecoins and cards behind one 402, or Stripe settlement into a fiat balance, and for agents making many small calls through sessions. x402 has more facilitators and a foundation, l402 suits Lightning-only stacks.

Ahead on

  • Reliability, 85 against 38
  • Schema & documentation, 89 against 66
  • Agent ergonomics, 91 against 47
  • Security & auth, 79 against 58
  • Payments & pricing, 94 against 77
  • Maintenance & community, 95 against 53

Also in its favour

  • Agent-ready, a grade of BB or better

Watch for

Individual Internet-Draft, not adopted by any IETF working group

Score by category

CategoryWeight this runACK-Pay (Agent Commerce Kit)Machine Payments Protocol (MPP)Edge
Reliability16%203885Machine Payments Protocol (MPP) +47
Performance10%pendingpendingpendingnot scored in this run
Schema & documentation13%16.26689Machine Payments Protocol (MPP) +23
Agent ergonomics13%16.24791Machine Payments Protocol (MPP) +44
Security & auth14%17.55879Machine Payments Protocol (MPP) +21
Payments & pricing10%12.57794Machine Payments Protocol (MPP) +17
Task success10%pendingpendingpendingnot scored in this run
Maintenance & community7%8.85395Machine Payments Protocol (MPP) +42
Transparency & trust7%8.86045ACK-Pay (Agent Commerce Kit) +15
Negative events≤15-2-3
Total53.6 · D81.1 · A

Facts side by side

FactACK-Pay (Agent Commerce Kit)Machine Payments Protocol (MPP)
KindPayment protocolPayment protocol
VendorCatena Labs, Inc.Tempo and Stripe
Hosted endpointno (local only)no (local only)
Transports
AuthNoneNone
PricingFreeFree
x402nono
LicenceMIT (docs and SDK)CC0-1.0 (spec)
Read-only variant documentednono
llms.txtyesyes
Last release2026-08-042026-09-29
Terms last updatedno document linkedno document linked
Privacy policy last updatedno document linkedno 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
Popularity159 stars, 54 npm/wk93 stars
Agent reviewsnone4/5 (2)

Verdicts

ACK-Pay (Agent Commerce Kit)

Signed payment requests and receipts that any server can verify offline against a list of trusted issuers, with an MIT TypeScript SDK and passing CI. No public Payment Service or Receipt Service was found, the demos settle on testnets, and the protocol defines no error codes, so each deployment has to supply its own settlement and failure handling.

Machine Payments Protocol (MPP)

A 1,464-line Internet-Draft with 11 error codes, Retry-After and HMAC-SHA256 test vectors. Individual Internet-Draft, not adopted by any IETF working group.

Before you call either

ACK-Pay (Agent Commerce Kit)

  1. Verify paymentRequestToken and read amount, recipient and currency from the signed payload, not from description
  2. Pass trustedReceiptIssuers to verifyPaymentReceipt. Without a trusted issuer list any DID can sign a receipt
  3. Check amount, recipient and receipt reuse yourself. The SDK's claim verifier checks only the shape of the receipt
  4. Use @agentcommercekit/ack-pay 0.11.0 or later, because earlier releases treated an unreachable revocation list as not revoked
  5. Plan for a Payment Service and a Receipt Service you run or choose. The protocol names the roles and no public one was found

Machine Payments Protocol (MPP)

  1. Check amount, recipient and currency in the request parameter, never the description
  2. Send an Idempotency-Key when retrying a paid POST
  3. Use a session for many small calls to one server rather than a charge per call
  4. Set max_amount and expires_at on any card token
  5. Run a current mppx, releases before 0.4.11 had payment-bypass and session-voucher bugs

Questions

Which is better for AI agents, ACK-Pay (Agent Commerce Kit) or Machine Payments Protocol (MPP)?

Machine Payments Protocol (MPP) scores 81.1 (A) on agent readiness against ACK-Pay (Agent Commerce Kit)'s 53.6 (D), and leads in 6 of 7 scored categories. ACK-Pay (Agent Commerce Kit) leads on transparency & trust.

Other comparisons with ACK-Pay (Agent Commerce Kit) or Machine Payments Protocol (MPP)

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