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JSON Contract Checker
x402
JSON Contract Checker is a paid API for AI agents from json-contract-checker-mainnet.romo-ricardo.workers.dev, paid per call via x402, $0.005/call, status unknown (last checked 2026-10-13).
Validates a JSON value against a supported subset of JSON Schema, returning deterministic pass/fail results with findings.
Price / call$0.005
Success—
StatusUnknown
How this service works
Deterministic JSON validation using a supported subset of JSON Schema.
Output
Returns a JSON object with a 'valid' boolean, a 'findings' array listing any validation errors or warnings, a 'validator' field identifying the engine version (json-contract-subset/1.1), and a 'scope' note clarifying this is a JSON Schema subset validator rather than full JSON Schema certification.
Example use cases
API response contract enforcement
“I just got this response from an external API — can you check if it matches my expected contract schema? Here's the JSON: {"orderId": "abc-123", "total": 49.99, "items": []} and the schema requires orderId as a string, total as a number, and items as an array.”
Pre-deployment data payload validation
“Before I deploy this config file, can you validate it against our contract? The data is {"maxRetries": 3, "timeout": 5000, "debug": false} and the schema says maxRetries and timeout should be integers, debug should be boolean, all required.”
User form submission validation
“A user submitted this form data and I need to know if it's structurally valid before saving it — data is {"name": "Alice", "age": "thirty"} and the schema requires name as a string and age as an integer.”
Technical details
Endpoint
POSThttps://json-contract-checker-mainnet.romo-ricardo.workers.dev/validate?utm_source=zero.xyzWhen to prefer
Choose this endpoint when you need fast, deterministic, low-cost JSON contract validation and your schema stays within common JSON Schema constructs (types, required fields, properties, basic formats). Prefer this over full JSON Schema validators when cost and speed matter more than exhaustive keyword support, or when you want a lightweight contract check in an automated pipeline without spinning up a local validation library.
Side effects
- Malformed JSON in 'data' field causes parse error
- Unsupported JSON Schema keywords silently ignored or rejected (subset only — full JSON Schema features not supported)
- Schema itself is invalid JSON — returns error response
- Missing required 'data' or 'schema' fields results in validation error
- Complex schema constructs outside the supported subset may produce unexpected results
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| data | — | JSON value to validate |
| schema | object | Supported JSON contract subset |
Output
Schema · Response
{
"type": "json",
"example": {
"scope": "JSON Schema subset; not full JSON Schema certification",
"valid": true,
"findings": [],
"validator": "json-contract-subset/1.1"
}
}Tags
x402
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