# JSON Schema Verifier

> 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.

## Facts

- Endpoint: POST https://fastapi-service-5ag4.onrender.com/verify/schema?utm_source=zero.xyz
- Price: $0.02/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-21
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/json-schema-verifier-2a291a54
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_TtJKlGI0iDx9H1eNtELNV

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability json-schema-verifier-2a291a54 -d '<json body>'
```

Example prompt: Can you validate this JSON payload against my schema and give me every violation — not just the first one? The data is the order object from our checkout API and the schema enforces draft-2020-12 rules including required fields, type constraints, and a sum_equals rule that the line item prices must add up to the order total.

## When to prefer this

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.

## Known failure modes

- 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

## 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.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "rules": {
   "anyOf": [
    {
     "type": "array",
     "items": {
      "type": "object",
      "title": "ConsistencyRule",
      "required": [
       "type",
       "field"
      ],
      "properties": {
       "type": {
        "enum": [
         "sum_equals",
         "gte",
         "lte",
         "exists_in",
         "unique"
        ],
        "type": "string",
        "title": "Type"
       },
       "field": {
        "type": "string",
        "title": "Field"
       },
       "value": {
        "anyOf": [
         {
          "type": "integer"
         },
         {
          "type": "number"
         },
         {
          "type": "string"
         },
         {
          "type": "null"
         }
        ],
        "title": "Value",
        "default": null
       },
       "equals": {
        "anyOf": [
         {
          "type": "integer"
         },
         {
          "type": "number"
         },
         {
          "type": "null"
         }
        ],
        "title": "Equals",
        "default": null
       },
       "values": {
        "anyOf": [
         {
          "type": "array",
          "items": {}
         },
         {
          "type": "null"
         }
        ],
        "title": "Values",
        "default": null
       },
       "in_field": {
        "anyOf": [
         {
          "type": "string"
         },
         {
          "type": "null"
         }
        ],
        "title": "In Field",
        "default": null
       },
       "tolerance": {
        "type": "number",
        "title": "Tolerance",
        "default": 1e-9,
        "minimum": 0
       },
       "other_field": {
        "anyOf": [
         {
          "type": "string"
         },
         {
          "type": "null"
         }
        ],
        "title": "Other Field",
        "default": null
       },
       "equals_field": {
        "anyOf": [
         {
          "type": "string"
         },
         {
          "type": "null"
         }
        ],
        "title": "Equals Field",
        "default": null
       }
      },
      "description": "One caller-supplied cross-field rule. Paths use dotted keys with '[]'\nas an array wildcard, e.g. 'items[].price' or 'order.total'.\n\n  sum_equals: sum of `field` values == `equals_field` value (or `equals`)\n  gte / lte:  `field` >= / <= `other_field` value (or `value`)\n  exists_in:  every `field` value is among `in_field` values (or `values`)\n  unique:     no d
… (truncated)
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/json-schema-verifier-2a291a54/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from fastapi-service-5ag4.onrender.com](https://www.zero.xyz/host/fastapi-service-5ag4.onrender.com/llms.txt)