AI Agent JSON Result Contract Checker

Check required JSON fields, exact values and numeric ranges; return pass/fail with a reproducible SHA-256 fingerprint.

$0.001 USDC on Base per paid request

Try fixed-data output first: Free demonstration

Live paid endpoint: POST https://penny-paid-batch-production.up.railway.app/api/proof-gate

Request JSON

{
  "result": {
    "status": "completed",
    "count": 2
  },
  "expectations": {
    "requiredPaths": [
      "status"
    ],
    "equals": {
      "status": "completed"
    },
    "numberRanges": {
      "count": {
        "min": 1,
        "max": 10
      }
    }
  }
}

When an agent would use this

Structured output checks between automated agent steps

Supported scope

Validates caller-supplied content only; a hash is not a signed independent execution attestation.

The paid endpoint returns an x402 HTTP 402 challenge to an unpaid request. An authorized buyer wallet must settle before fulfillment. A challenge or fixed-data demo does not prove an outside sale.

Machine-readable tasks · Live status checks · Developer quickstart · MCP server (POST)