ACK-Pay (Agent Commerce Kit) vs x402

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.

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).

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

x402

1. Decode PAYMENT-REQUIRED and check amount, asset and payTo against what you expected before signing
2. Use the upto scheme when the final price isn't known, and cap it
3. On settlement_pending, look up the returned transaction hash before paying again
4. Use a production facilitator for Base mainnet, x402.org/facilitator is testnet only
5. Give the agent its own wallet with a small balance, never a treasury key