x402 endpoint preflight

Endpoint

https://apiacre.com/v1/developer/x402-preflight

Send the JSON body below. An unpaid request returns HTTP 402 with a PAYMENT-REQUIRED header; an x402-compatible buyer signs the requirement and retries with PAYMENT-SIGNATURE.

Input example

{
  "url": "https://apiacre.com/v1/developer/openapi-audit",
  "method": "POST",
  "body": {
    "document": "{\"openapi\":\"3.1.0\",\"info\":{\"title\":\"Example\",\"version\":\"1\"},\"paths\":{}}",
    "format": "json"
  }
}

Response shape

View free static sample JSON

{
  "request_id": "018f1f54-7f38-7ba2-8dc3-5f90272d9f1a",
  "service": "developer.x402-preflight",
  "version": "1",
  "data": {
    "url": "https://apiacre.com/v1/developer/openapi-audit",
    "finalUrl": "https://apiacre.com/v1/developer/openapi-audit",
    "method": "POST",
    "statusCode": 402,
    "elapsedMs": 128,
    "compliant": true,
    "grade": "A",
    "score": 100,
    "gradeVersion": "apiacre-x402-preflight/1",
    "checks": [
      {
        "id": "http_402",
        "passed": true,
        "severity": "high",
        "message": "Return HTTP 402 before payment."
      },
      {
        "id": "header_decodes",
        "passed": true,
        "severity": "high",
        "message": "PAYMENT-REQUIRED decodes to a JSON object."
      },
      {
        "id": "x402_v2",
        "passed": true,
        "severity": "high",
        "message": "Set x402Version to the integer 2."
      },
      {
        "id": "caip2_network",
        "passed": true,
        "severity": "high",
        "message": "Use a valid CAIP-2 network identifier."
      },
      {
        "id": "resource_binding",
        "passed": true,
        "severity": "medium",
        "message": "Bind resource.url to the endpoint that returned the payment requirement."
      }
    ],
    "payment": {
      "version": 2,
      "acceptsCount": 1,
      "scheme": "exact",
      "network": "eip155:8453",
      "amount": "50000",
      "asset": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
      "payTo": "0xa0BFa4f07281c9b248DC3AED2217836BcA24869B"
    },
    "remediation": [],
    "checkedAt": "2026-08-09T00:00:00+00:00",
    "limitations": "One unpaid request only; no payment is signed and the target response is not retained."
  },
  "meta": {
    "duration_ms": 42,
    "cached": false,
    "sources": [],
    "warnings": []
  }
}

Try the payment challenge

curl -i -X POST 'https://apiacre.com/v1/developer/x402-preflight' \
  -H 'content-type: application/json' \
  --data '{"url":"https://apiacre.com/v1/developer/openapi-audit","method":"POST","body":{"document":"{\"openapi\":\"3.1.0\",\"info\":{\"title\":\"Example\",\"version\":\"1\"},\"paths\":{}}","format":"json"}}'