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JSON Schema Verifier
x402
JSON Schema Verifier is a paid API for AI agents from fastapi-service-5ag4.onrender.com, paid per call via x402, $0.02/call, status unknown (last checked 2026-10-21).
Validates any JSON value against a caller-supplied JSON Schema (draft-04 through 2020-12) and returns all violations found, plus optional cross-field consistency checks.
Price / call$0.02
Success—
StatusUnknown
How this service works
Independently verify an agent's output before you pay: an invoice or any deliverable, checked against your JSON Schema and rules like sums matching totals. Pass/fail, % passed, fix hints and a signed receipt. $0.02 USDC, no signup, x402 v2.
Output
A list of every schema violation found in the submitted JSON value, including the JSON path, violated constraint, expected vs actual values, and any cross-field rule or bound violations reported as informational flags. Returns an empty violations list if the data is fully valid.
Example use cases
Validating agent tool output
“The tool-calling agent just returned a JSON object claiming to be a structured itinerary. Can you run it through my JSON Schema — draft-07, with required fields 'destination', 'dates', and 'activities' as an array — and list every field that's missing or has the wrong type?”
Enforcing API response contracts
“Our upstream payments API returned this JSON response. Please validate it against our expected schema (draft-2020-12) and tell me every violation so I know whether it's safe to process — I need all errors, not just the first one.”
Config file pre-deployment check
“Before we deploy, can you validate this environment config JSON against our infrastructure schema? It should enforce that 'max_replicas' is always greater than or equal to 'min_replicas', and that every 'region' value exists in our allowed regions list — flag every inconsistency you find.”
Technical details
Endpoint
POSThttps://fastapi-service-5ag4.onrender.com/verify/schema?utm_source=zero.xyzWhen to prefer
Choose this endpoint when you need exhaustive validation — all violations, not just the first — against a caller-supplied JSON Schema across any supported draft (04 through 2020-12), especially when you also need cross-field consistency checks (sum_equals, gte, lte, exists_in, unique) in a single call. Prefer it over client-side validators when the agent environment lacks a native JSON Schema library, or when you need a neutral third-party validation result for audit purposes.
Side effects
- Invalid or unparseable JSON Schema supplied — returns a schema parse error
- Unsupported JSON Schema draft version — returns unsupported draft error
- Malformed input JSON — returns parse error before validation begins
- Too many cross-field rules supplied (over 50) — returns limit exceeded error
- Network timeout on render.com cold start — returns 504 or connection error
- Payment not received or insufficient — returns 402 Payment Required
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| rules | — | Optional cross-field rules: sum_equals, gte, lte, exists_in, unique (duplicate detection). Violations are reported as informational flags only. |
| bounds | — | Optional per-field min/max, keyed by dotted path with '[]' array wildcard (e.g. 'items[].price'). Numbers or ISO-8601 dates. Violations are reported as informational flags only. |
| task_id | string | |
| agent_id | — | |
| expected_schema | object | |
| submitted_output | — | |
| strict_content_check | boolean | Opt-in. When true, any string in submitted_output containing control characters (e.g. null bytes) or embedded HTML/script markup makes the result 'fail'. When false (default) this is not checked at all. |
Tags
x402
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