Payment vs. service
A claimed 402 → VERIFY → SETTLE → DELIVER sequence may look consistent while the service failed. This tool cannot authenticate provider events, network finality, job readiness, or refund/credit records.
X402 PAYMENT OPS · EVIDENCE BEFORE RE-TRY
A payment said settled.
Was anything delivered?
Model a fictional x402 payment timeline before your agent risks repeating a charge. Flag claimed settlements with no delivery record, multiple payment labels for one order, price mismatches, and unsafe retry sequences. This is local educational triage, not an on-chain verifier.
✓ No account or signup✓ No wallet connection✓ No API calls or uploads✓ 32 synthetic events max
01 / TRY ONE SCENARIO
Runs on this devicePayment event timeline
Do not paste real provider logs, customer data, transaction signatures, API credentials or wallet addresses. Use invented labels such as jobA and payA, and hypothetical six-decimal USDC amounts. Paste nothing you lack permission to share—even though this page itself makes no outbound network requests.
Accepted kinds: QUOTE, VERIFY, SETTLE, DELIVER, RETRY, REPLAY_REJECTED, PRICE_CHANGED, REJECT. All event labels must be short, invented identifiers. Event order is list order.
Findings
NOT PAYMENT PROOFEvery result uses only supplied labels. A 200 response, a successful verification, or a claimed settlement is not independently verified payment or delivery. Review provider receipts, original buyer authorization, and unique finalized transaction evidence separately. Never automatically re-sign because this checker flags an error.
BEFORE YOU SIGN · MULTIPLE PRICES / SUBSCRIPTION PLANS
Do the plan quote and verifier agree?
One real independent x402 developer reported a production-blocking mismatch: a 9.000000 USDC prepaid access quote was verified against the application's unrelated 0.005000 USDC per-call default, even though the 402 quote test was green. Read that developer's firsthand case ↗. Our sample models the arithmetic only and is neither their product nor a live middleware test.
This tool does not connect to a payment service. Manually type invented plan labels and the amounts that a server UI, 402 challenge, and verification seam would use, all as six-decimal USDC atomic unit strings. A mismatch warns that the value passed to the verifier may not match what the buyer was asked to sign.
Only synthetic short plan names and decimal atomic USDC amounts (e.g. 9000000 means 9.000000 USDC). No wallet address, tx hash, customer data, or actual request headers.
Pre-sign findings
This is not actual settlement evidence. To verify a merchant integration, test your own server middleware's amount-argument seam using a fake verifier spy in your own authorized CI; never spend crypto to make a test green.
Does the free result match your experience?
If a warning was wrong or a case is missing, send a public, non-sensitive developer feedback issue ↗. This is voluntary and requires a GitHub account. The optional form asks what you actually tried and whether a separate 29 USDC human review could matter; it does not purchase anything. Never submit wallets, signed payloads, client logs or secrets. Independent human feedback received so far: none verified.
02 / WHAT IT CANNOT DO
Safer retry decisions
When a response is lost, recover the original order receipt using the merchant's documented idempotency and support flow. Do not sign a second transfer until its necessity is independently proven.
Payment amounts
Use synthetic six-decimal USDC atomic units. A mismatch might be a valid account credit rather than overcharging; the tool does not verify the chain, recipient, token contract or quote signature.
03 / OPTIONAL INDEPENDENT ENGINEERING
Have a public x402 failure to reproduce?
Request an individually agreed written QA scope, fixed 29 native Circle Base USDC for one buyer-authorized, publicly shareable HTTP route and synthetic non-paying retry cases. Only if accepted: bounded reproduction, precise observed results and a proposed test matrix. This is a quote, not an instant checkout or safety audit.
No live payment, private logs, merchant authentication or automatic scanning without separately agreed authorization. AI-assisted single operator based in South Korea; acceptance criteria, payment recipient, timing and refund terms agreed in writing before work.
Request a private x402 QA scope — no Google login required ↗The separate Google-hosted form asks for a reply email, one optional PUBLIC route, a non-sensitive problem description, and nonbinding interest in FREE help or the existing 29-USDC review. Submitting is NOT an order or authorization to run tests, and Google may process submitted information. Never include wallet keys, signed x402 payloads, transaction/customer records, auth tokens or private logs. No personal data leaves this browser-local free checker until you independently choose to open and submit the Google form.
Request a non-secret QA scope by email →View the separate 29 USDC fixed-price marketplace offer ↗ · The external platform handles any buyer-initiated purchase; scope, escrow, payout and refund rules must be independently confirmed before ordering. This page charges nothing, and the offer has no verified previous customers.
Other free single-owner tools
VM1 x402 quote / CORS / header budget ↗VM3 x402 v1/v2 quote checks ↗VM2 merchant x402.json preflight ↗VM2 private browser-only CSV QA ↗One beneficial owner runs these tools. Links are alternatives, not independent customer endorsements.