Live x402 software · original same-owner VM5 merchant · 20 Oct 2026

Find CSV structure problems before your agent imports the file.

When you have a CSV you are authorized to inspect, use a transparent machine-payable API to check row shape, duplicated entries, empty values, invalid-looking fields, and spreadsheet formula risks. A valid unpaid request returns standard HTTP 402 — 0.005 native Circle USDC on Base per completed paid call. No customer data is ever needed to view the free demo.

Try the free local CSV checker first

The original interactive browser-only checker detects uneven rows, duplicate records, missing or duplicate headers, empty cells and spreadsheet-formula patterns without uploading your CSV or connecting a wallet. Its results are a limited preview, not equivalent to the paid API and not a purchase receipt.

Run the free private CSV checker →

Runnable payment-handshake preflight

This exact example uses invented .invalid email addresses. It does not send a payment signature. If the request body is valid, the service returns HTTP 402 Payment Required; the response includes the payment terms to be accepted by your own authorized x402 client. Running the command alone cannot buy the report.

curl -i --request POST \
  'https://vm5-openapi-x402.onrender.com/v1/csv-preflight' \
  --header 'Content-Type: application/json' \
  --data '{"csvText":"email,amount,date,note\na@example.invalid,12.5,2026-10-20,paid\na@example.invalid,12.5,2026-10-20,paid\nb@example.invalid,not-a-number,2026-13-99,=1+1","expectedColumns":["email","amount","date","note"]}'

Fresh read-only smoke evidence on 20 October 2026: the example was accepted for payment negotiation (HTTP 402 with PAYMENT-REQUIRED), while an empty CSV was rejected HTTP 400 without a payment challenge. Those responses show billing is gated; neither proves a successful paid delivery.

Scope and operating limits

• UTF-8 JSON body; CSV text at most 32 KiB; at most 500 data rows and 40 columns.
• Optional expected column names can make missing or reordered fields easier to spot.
• Paid results report structure and issue locations rather than raw source rows. Infrastructure-level request logging may still apply; do not send passwords, wallet seeds or confidential customer records.
• The service flags patterns; it cannot certify database integrity, privacy-law compliance, merchant identity, or production data safety.
• Network: eip155:8453; asset: native Circle USDC on Base. Only the buyer's own wallet authorizes payment.

Real buyer integration: inspect the exact quote, then choose whether to pay

For agent developers who want to call the customer-input POST, we publish a runnable MIT-licensed original, pinned x402 v2 buyer client with tests. A normal run checks the signed-payment terms without any wallet or charge. An independently consenting external customer can opt in to a real 0.005 USDC purchase using their own low-value buyer wallet. It refuses a changed token, recipient, chain, method, resource or price before signing. No owner-funded purchase, working customer order or final USDC receipt is asserted by this SDK sample.

View buyer SDK + offline test cases ↗

New optional independent buyer web checkout (beta)

Want to buy without installing Node? Use the 0.005 USDC browser buyer interface to preview the real POST x402 quote first, then optionally connect an independently funded Base-compatible browser wallet and explicitly authorize a single charge. It strictly rejects changes to network, native Circle USDC token, pay-to address, exact amount, method or resource before an EIP-712 signature. It does not use the operator's MetaMask or pre-authorize purchases. The quote preview sends the buyer's CSV to the hosted service even if they do not buy. No independently completed real wallet purchase or settlement through this browser interface is claimed; the initial signed-money path is still beta and should be reviewed before use.

Open buyer checkout (optional, 0.005 USDC) →

Know which endpoint is useful

The separate GET /v1/csv-report also costs 0.005 USDC but reports on a predefined synthetic example. To inspect your own actual CSV, use POST /v1/csv-preflight instead. Neither requires registration to view the unpaid 402 payment challenge.

Provenance, ownership and transparent limitations

This is an original, AI-assisted software service owned by one human beneficiary and hosted in the same owner's VM5 x402 merchant. This VM3 page is a sales and integration guide, not another merchant, not a second operator, and not a representation of third-party customer orders. A previously observed Circle USDC wallet receipt is not attributed to this specific POST endpoint without request-level proof. Refund and delivery terms are governed by the actual agreed provider payment flow.

Other original QA services · Why 402 responses are not sales · Reproducible owner-operated QA sample