CHECK BEFORE SIGNING

Put your policy
next to the payment.

Send an x402 v2 requirement and your intended recipient and price limits. The API checks the quote and returns explainable issue codes. Your application decides whether to pay the original seller.

POST /api/lint

{
  "paymentRequired": { "x402Version": 2, "accepts": [ ... ] },
  "policy": {
    "allowedPayTo": ["0x...your trusted recipient..."],
    "maxAmountUsd": 0.05,
    "maxTimeoutSeconds": 60
  }
}

Price: $0.001 USDC per API call. The browser preview runs locally for free. Use the paid API when a consistent service boundary and JSON contract fit your workflow.

Supported scope

Only x402 v2 exact payments in native USDC on Base mainnet are evaluated. Custom allowlists cannot turn another token into USDC or alter its decimals. Amounts are bounded to uint256 and compared in atomic units.

Use the verdict

• pass: the quote fits the supplied structural and policy checks.
• review: warnings need a caller decision, such as an unpinned recipient.
• reject: block the payment and inspect issue codes.

A pass does not prove the seller is legitimate. Supply a recipient allowlist checked out of band. Your guard should pin 402 Guard’s own fee and recipient locally rather than relying on a second paid service to check its quote.

Get the full input example · Get fixture outputs · OpenAPI schema