JSON Schema Generator
Generate JSON Schema from sample JSON for apps, APIs, and AI workflows
JSON Input
JSON Schema Output
Build a JSON Schema from a real payload
Writing JSON Schema by hand is slow and easy to get wrong. Generating one from a sample document gives you a solid starting point — types inferred from values, required fields detected from presence, and nested objects expanded — that you can tighten with enums, formats, and constraints before shipping.
Use the generator when you need to
Bootstrap a contract for a new API
Take a sample response and generate a Draft 2020-12 schema you can refine with proper validation rules.
Validate AI structured output
Lift the schema from a known-good model response so downstream validation has something concrete to enforce.
Document the shape of a payload
Use the generated schema as living documentation of what your service produces or expects.
How to generate a JSON Schema
- 1
Paste a representative sample JSON document.
- 2
Click Generate to produce a Draft 2020-12 schema with inferred types and required fields.
- 3
Refine the schema with enums, patterns, and explicit required arrays before adopting it.
Keep going
Validate against the generated schema
Check real payloads against the schema you just generated.
Wrap for OpenAI or Anthropic
Adapt the schema for OpenAI Structured Outputs, Anthropic tools, or MCP definitions.
Generate TypeScript types
Pair runtime validation with compile-time types from the same sample.
Generate matching mock data
Produce fake records that satisfy the schema for tests and prototypes.
Common schema-generation workflows
Generate the schema once, commit it to source control, and reject deviations in CI.
Use the generated schema to enforce that model output matches what your handler expects.
Quickly produce schemas for existing payloads and start enforcing them in stages.
Related Tools
Structured Output Schema Builder
Generate OpenAI, Anthropic, MCP, or plain JSON Schema wrappers from sample output
JSON Schema Validator
Validate JSON, LLM outputs, and tool inputs against a JSON Schema
Anthropic Tool Input Builder
Build Claude tool definitions with `input_schema` from sample JSON input
JSON to TypeScript
Generate TypeScript interfaces and types from JSON
Frequently Asked Questions
JSON Schema is a vocabulary for describing the structure and validation rules of JSON data. It defines what properties are allowed, their types, required fields, and constraints like min/max values or string patterns.
Paste a sample JSON document and click Generate. The tool analyzes the structure and types to produce a draft JSON Schema that validates documents with the same shape as your sample.
The tool generates schemas compatible with JSON Schema Draft 2020-12 (the latest draft), which is supported by most validation libraries including Ajv, jsonschema, and everit-json-schema.
Yes. The generated schema can be used directly with schema validation libraries in any language, in OpenAPI/Swagger definitions, or with form validation tools to ensure incoming data matches the expected structure.
Yes. Generated schemas are a strong starting point for OpenAI Structured Outputs, Anthropic tool input_schema objects, MCP inputSchema definitions, and any workflow where a model must return predictable JSON. You may still want to tighten additionalProperties, enums, and required fields before production use.