Validate JSON against a JSON Schema

Validates instance against schema with @cfworker/json-schema (an interpreter: no code generation). The draft comes from draft, else from the schema's $schema, else 2020-12. Returns valid and, for an invalid instance, each error with the instance location and keyword location as JSON Pointers, the location of the keyword in the schema document (after following $ref), and a message; leaf: false marks summary errors (from properties, items, $ref, anyOf, …) that are followed by the specific errors beneath them. An invalid instance is a successful response with valid: false. Before validating, the schema is checked for usability (keyword types, regular expressions, unresolved references); problems are a 422 error. Only local references resolve: $ref to a remote URL is never fetched (the server makes no network requests); embed such schemas under $defs with their $id. format is asserted for the formats listed in the docs. $dynamicRef is not supported. At most 1000 errors are returned.

Browser version (runs locally): JSON Schema Validator.

Parameters

Also accepted on every endpoint: format (json | text). Parameters may come from the query string, a JSON object body, an urlencoded or multipart form, or (for input) a text/plain body.

Response 200 application/json

Text output (format=text, text/plain): valid, or invalid followed by one line per leaf error: <instanceLocation or /> <message>.

Errors

Errors are JSON: {"error": "<message>", "code": "<code>", "param": "<name>"?}.

Behaviour

• Idempotent: the same arguments always return the same result.
• Requires a client ID and secret (authentication). Each call is recorded as one metadata row against your client ID; inputs and outputs are never stored or logged. Responses carry cache-control: no-store.
• CORS: any origin may call this endpoint from a browser, using your credentials.

Examples

Responses below were produced by running each request through this code at build time. Long strings are shortened.

curl -X POST 'https://util.caruana.me/api/json/schema/validate' \
  -H 'content-type: application/json' \
  -d '{"schema":"{\"$schema\":\"https://json-schema.org/draft/2020-12/schema\",\"type\":\"object\",\"required\":[\"id\",\"email\"],\"properties\":{\"id\":{\"type\":\"integer\",\"minimum\":1},\"email\":{\"type\":\"string\",\"format\":\"email\"},\"tags\":{\"type\":\"array\",\"items\":{\"type\":\"string\"},\"uniqueItems\":true}},\"additionalProperties\":false}","instance":"{\"id\":0,\"tags\":[\"a\",\"a\"],\"extra\":true}"}'

{
  "valid": false,
  "draft": "2020-12",
  "draftSource": "$schema",
  "errorCount": 7,
  "errors": [
    {
      "instanceLocation": "",
      "keyword": "required",
      "keywordLocation": "/required",
      "schemaLocation": "/required",
      "message": "Instance does not have required property \"email\".",
      "leaf": true
    },
    {
      "instanceLocation": "",
      "keyword": "properties",
      "keywordLocation": "/properties",
      "schemaLocation": "/properties",
      "message": "Property \"id\" does not match schema.",
      "leaf": false
    },
    {
      "instanceLocation": "/id",
      "keyword": "minimum",
      "keywordLocation": "/properties/id/minimum",
      "schemaLocation": "/properties/id/minimum",
      "message": "0 is less than 1.",
      "leaf": true
    },
    {
      "instanceLocation": "",
      "keyword": "properties",
      "keywordLocation": "/properties",
      "schemaLocation": "/properties",
      "message": "Property \"tags\" does not match schema.",
      "leaf": false
    },
    {
      "instanceLocation": "/tags",
      "keyword": "uniqueItems",
      "keywordLocation": "/properties/tags/uniqueItems",
      "schemaLocation": "/properties/tags/uniqueItems",
      "message": "Duplicate items at indexes 0 and 1.",
      "leaf": true
    },
    {
      "instanceLocation": "",
      "keyword": "additionalProperties",
      "keywordLocation": "/additionalProperties",
      "schemaLocation": "/additionalProperties",
      "message": "Property \"extra\" does not match additional properties schema.",
      "leaf": false
    },
    {
      "instanceLocation": "/extra",
      "keyword": "false",
      "keywordLocation": "/additionalProperties",
      "schemaLocation": "/additionalProperties",
      "message": "The schema here is false: no value is allowed at this location.",
      "leaf": true
    }
  ],
  "warnings": []
}

{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "tools/call",
  "params": {
    "name": "json_schema_validate",
    "arguments": {
      "schema": "{\"$schema\":\"https://json-schema.org/draft/2020-12/schema\",\"type\":\"object\",\"required\":[\"id\",\"email\"],\"properties\":{\"id\":{\"type\":\"integer\",\"minimum\":1},\"email\":{\"type\":\"string\",\"format\":\"email\"},\"tags\":{\"type\":\"array\",\"items\":{\"type\":\"string\"},\"uniqueItems\":true}},\"additionalProperties\":false}",
      "instance": "{\"id\":0,\"tags\":[\"a\",\"a\"],\"extra\":true}"
    }
  }
}

curl -X POST 'https://util.caruana.me/api/json/schema/validate' \
  -H 'content-type: application/json' \
  -d '{"schema":"{\"$defs\":{\"port\":{\"type\":\"integer\",\"minimum\":1,\"maximum\":65535}},\"type\":\"array\",\"items\":{\"$ref\":\"#/$defs/port\"}}","instance":"[80, 443]"}'

{
  "valid": true,
  "draft": "2020-12",
  "draftSource": "default",
  "errorCount": 0,
  "errors": [],
  "warnings": []
}

{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "tools/call",
  "params": {
    "name": "json_schema_validate",
    "arguments": {
      "schema": "{\"$defs\":{\"port\":{\"type\":\"integer\",\"minimum\":1,\"maximum\":65535}},\"type\":\"array\",\"items\":{\"$ref\":\"#/$defs/port\"}}",
      "instance": "[80, 443]"
    }
  }
}