JSON Schema API

Validate JSON against a JSON Schema or generate a draft 2020-12 schema from sample data. Detailed error paths, format detection, free and browser-based.

The JSON Schema is also available as a free REST API. Send a POST request with a JSON body to https://dot.tools/api/tools/json-schema — no authentication, no API key, CORS enabled. Successful calls return { "ok": true, "result": { … } }; failures return HTTP 400 or 422 with an error body.

Request body

Field	Type	Required	Description
`mode`	"validate" \| "generate"	required	validate: check an instance against a schema. generate: infer a draft 2020-12 schema from a sample document.
`instance`	string	required	The JSON document to validate (max 1 MB in validate mode) or to infer a schema from (max 5 MB in generate mode).
`schema`	string	optional	Required in validate mode: the JSON Schema (draft 2020-12) as JSON text, max 1 MB. Local $refs only; remote refs are never fetched.

Response

Field	Type	Required	Description
`mode`	"validate" \| "generate"	required	The mode that was executed.
`valid`	unknown	required	Validate mode: whether the instance conforms. format-keyword failures do not affect this.
`schemaError`	unknown	required	Validate mode: why the schema itself could not be used (invalid JSON, uncompilable, unresolved remote $ref).
`errors`	object[]	required	Validate mode: instance-validation errors, capped at 100 entries.
`errorCount`	unknown	required	Validate mode: total instance-validation errors before the cap.
`formatWarnings`	object[]	required	Validate mode: format-keyword failures, reported as annotations only (capped at 100).
`schema`	unknown	required	Generate mode: the inferred draft 2020-12 schema, pretty-printed.

Example request

curl -X POST https://dot.tools/api/tools/json-schema \
  -H 'Content-Type: application/json' \
  -d '{
  "mode": "generate",
  "instance": "{\n  \"id\": \"3f6b0f5e-8c1d-4a2b-9e7c-1d2f3a4b5c6d\",\n  \"name\": \"Ada Lovelace\",\n  \"email\": \"ada@analytical.engineer\",\n  \"created_at\": \"1843-09-09T12:30:00Z\",\n  \"website\": \"https://example.com/ada\",\n  \"level\": 9,\n  \"score\": 98.5,\n  \"active\": true,\n  \"address\": {\n    \"city\": \"London\",\n    \"zip\": \"EC1\"\n  },\n  \"roles\": [\n    \"engineer\",\n    \"mathematician\"\n  ],\n  \"nickname\": null\n}"
}'

Sample response

{
  "ok": true,
  "result": {
    "mode": "generate",
    "valid": null,
    "schemaError": null,
    "errors": [],
    "errorCount": null,
    "formatWarnings": [],
    "schema": "{\n  \"$schema\": \"https://json-schema.org/draft/2020-12/schema\",\n  \"type\": \"object\",\n  \"properties\": {\n    \"active\": {\n      \"type\": \"boolean\"\n    },\n    \"address\": {\n      \"type\": \"object\",\n      \"properties\": {\n        \"city\": {\n          \"type\": \"string\"\n        },\n        \"zip\": {\n          \"type\": \"string\"\n        }\n      },\n      \"required\": [\n        \"city\",\n        \"zip\"\n      ]\n    },\n    \"created_at\": {\n      \"type\": \"string\",\n      \"format\": \"date-time\"\n    },\n    \"email\": {\n      \"type\": \"string\",\n      \"format\": \"email\"\n    },\n    \"id\": {\n      \"type\": \"string\",\n      \"format\": \"uuid\"\n    },\n    \"level\": {\n      \"type\": \"integer\"\n    },\n    \"name\": {\n      \"type\": \"string\"\n    },\n    \"nickname\": {\n      \"type\": \"null\"\n    },\n    \"roles\": {\n      \"type\": \"array\",\n      \"items\": {\n        \"type\": \"string\"\n      }\n    },\n    \"score\": {\n      \"type\": \"number\"\n    },\n    \"website\": {\n      \"type\": \"string\",\n      \"format\": \"uri\"\n    }\n  },\n  \"required\": [\n    \"active\",\n    \"address\",\n    \"created_at\",\n    \"email\",\n    \"id\",\n    \"level\",\n    \"name\",\n    \"nickname\",\n    \"roles\",\n    \"score\",\n    \"website\"\n  ]\n}"
  }
}

Use the free JSON Schema in your browser, read the JSON Schema guide, or import the full OpenAPI specification.