{"uid":"cap_BQawEs3MpLmhtsPBCoc3N","slug":"delx-commerce-x402-payment-nonce-check-e94b0ee1","name":"Delx Commerce — X402 Payment Nonce Check","description":"Pay-per-result APIs for agents. No signup. Exact price. Verifiable delivery. USDC on Base + Solana via x402.","url":"https://commerce.delx.ai/api/v1/x402/x402-payment-nonce-check?utm_source=zero.xyz","method":"POST","headers":{},"bodySchema":{"type":"object","properties":{"nonce":{"type":"string","maxLength":8192,"description":"Nonce supplied to X402 Payment Nonce Check; used only for this bounded calculation and processed in memory without retention."},"seen_nonces":{"type":"array","items":{"type":"string","maxLength":8192},"maxItems":256,"description":"Seen Nonces supplied to X402 Payment Nonce Check; used only for this bounded calculation and processed in memory without retention."},"minimum_length":{"type":"integer","description":"Minimum Length supplied to X402 Payment Nonce Check; used only for this bounded calculation and processed in memory without retention."}}},"responseSchema":{"type":"json","example":{"result":{"reused":false,"accepted":true,"nonce_length":18},"schema":"delx/util-x402-payment-nonce-check/v1","status":"pass","evidence":{"retained":false,"input_sha256":"5b10e7096699f6b6a1dcbc3414bdd28a9a8deeb87ccf9e505917b2a855abe5e2","external_calls":0},"operation":"delivery_contract:x402_payment_nonce_check"}},"example":null,"exampleRequest":null,"tags":["x402"],"displayCostAmount":"0.001","displayCostAsset":"USDC","priceDynamic":false,"priceHint":null,"priceStatus":"priced","priceSource":"probe","requiresHandshake":false,"reviewCount":0,"rating":{"score":"0.00","successRate":"0.00","reviews":0,"stars":null,"state":"unrated"},"availabilityStatus":"unknown","priceObserved":null,"sessionDeposit":null,"pricing":{"kind":"static","summary":"$0.001/call","primary":{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.001","per":"call","confidence":"exact"},"accepted":[{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.001","per":"call","confidence":"exact"}]},"paymentMethods":[{"uid":"pm_ZjHG2_nJoeI_aV9yS3kZq","protocol":"x402","methodType":"crypto","chain":"base","mode":"charge","costAmount":"0.001","costPer":"request","priority":0,"asset":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","unit":"request","depositMicros":null,"planRef":null}],"brandName":null,"brandSlug":null,"brandBaseUrl":null,"brandDocsUrl":null,"whatItDoes":"Validates whether an X402 payment nonce is fresh (not reused) and meets minimum length requirements, returning acceptance status with verifiable evidence.","exampleAgentPrompt":"Check if the nonce 'a7f3k92mxq1b4p8r' is fresh and not already in this list of seen nonces ['x9q2z', 'b4k1m7n', 'a7f3k92mxq1b4p8r'], with a minimum length of 12 characters.","exampleUseCases":[{"title":"Replay attack prevention in agent payment flow","prompt":"Before I finalize this x402 payment, check whether nonce 'tR7xQ2mNpL9w' is already in my list of seen nonces ['aB3dE5fG', 'hI7jK9lM'] and make sure it's at least 10 characters long."},{"title":"Nonce freshness check before USDC micropayment","prompt":"I'm about to accept a USDC micropayment via x402. Verify that the nonce 'zP4qR8sT6uV2' hasn't been used before — my seen nonces are ['nA1bC3dE', 'fG5hI7jK'] — and confirm it meets a minimum length of 8."},{"title":"Batch session nonce deduplication for agent fleet","prompt":"My agent received a payment nonce 'mX5yZ0aB2cD4' and I need to confirm it's not a replay against my current seen nonces list ['eF6gH8iJ', 'kL1mN3oP', 'qR5sT7uV']; minimum acceptable length is 16."}],"resultDescription":"Returns a JSON object indicating whether the nonce was reused (reused: bool), whether it was accepted (accepted: bool), and its measured length (nonce_length: int). Also includes evidence fields: whether inputs were retained (retained: false), a SHA-256 hash of the input for auditability, and a count of external calls made (always 0, confirming no data left the system). Operation and schema identifiers are included for traceability.","failureModes":["Nonce exceeds maxLength of 8192 characters — request rejected","seen_nonces array exceeds 256 items — request rejected","Missing nonce field — validation cannot proceed","Invalid type for minimum_length (non-integer) — schema validation error","Network timeout or service unavailability — HTTP 5xx response"],"whenToPreferThis":"Choose this endpoint when you need a lightweight, verifiable, privacy-preserving nonce uniqueness check within an x402 payment flow. It processes entirely in memory with no data retention and provides a SHA-256 evidence hash for auditability — making it ideal for agents that need cryptographic proof of the check without exposing payment data externally. Prefer it over custom nonce deduplication logic when you need a pay-per-result, no-signup solution that integrates natively with the x402 protocol on Base or Solana.","instructions":null,"reviewSummary":null,"reviewSummaryHighlights":null,"reviewSummaryConcerns":null,"reviewSummaryGeneratedAt":null,"activationCount":0,"lastUsedAt":null,"lastSuccessfullyRanAt":null,"lastHealthCheckAt":"2026-10-01T00:45:53.051Z","isFirstParty":false,"canonicalSlug":"delx-commerce-x402-payment-nonce-check-e94b0ee1"}