For API builders and AI workflow teams
SchemaSmith is a free JSON Schema generator that converts pasted JSON into an editable Draft 2020-12 schema. Validate payloads, create mock JSON, repair syntax, copy results, and download files in one place. Your input stays in the browser and is not sent to a server.
No signup required. Save the current schema, source example, mock JSON, and validation result locally.
Free JSON Schema generator
Paste a JSON example on the left, such as an API response with id, name, and roles, then select “Generate schema.” The editable Draft 2020-12 output on the right includes inferred types, required fields, nested objects, arrays, and common string formats.
Paste or edit a JSON payload, then choose an action. Nothing in these editors is sent over the network.
Privacy boundary: parsing, inference, validation, fixture generation, repair, copying, and export happen with client-side JavaScript.
Built for real payload work
Each tool answers a practical question: what shape does this data have, why did validation fail, and what fixture can I use next?
Infer objects, arrays, required properties, primitive types, and common string formats from the payload you already have.
Validate against the schema in the editor and receive path-specific errors that point to the property or array item that needs attention.
Create mock JSON from the current schema, export the working bundle, or run the included MCP server from a compatible AI client.
How to use SchemaSmith
Use a real example with the fields and nested values your application expects. The data remains in the browser.
Infer a starting contract, then edit constraints such as required fields, formats, ranges, patterns, or allowed values.
Test the payload, generate a fixture for development, download the bundle, or bring the workflow into an MCP-compatible client.
JSON Schema FAQ
Paste a representative JSON example into the left editor and select “Generate schema.” An editable Draft 2020-12 JSON Schema appears on the right with inferred types, required fields, arrays, and nested objects.
No. The workbench uses client-side JavaScript for parsing, schema inference, validation, mock generation, repair, and export. Your payload is not uploaded by these tools.
It infers null, boolean, integer, number, string, array, and object types; nested properties; required keys; merged array item shapes; and common email, URI, date, and date-time formats. You can edit the result before validating or exporting it.
The validator supports core type and property checks, local JSON Pointer references, required fields, additional properties, enum, const, allOf, anyOf, oneOf, not, conditional schemas, string and numeric constraints, array limits, unique items, contains, pattern properties, and dependent required fields.
It prefers const, default, example, and enum values when present. Otherwise it creates deterministic values from the property name, type, format, and minimum constraints. The result is intended as a practical fixture that you can review and adapt.
It is a readable Node.js file generated by this page. It exposes local JSON schema inference, validation, fixture, and repair tools through the Model Context Protocol. Download the file, review it, and add its absolute path to a compatible client.
Yes. When the current JSON and schema are valid, select a download button to save schemasmith-bundle.json with the schema, source example, generated mock JSON, and validation result. No signup or email address is required.
Download schemasmith-bundle.json with the current schema, source JSON example, generated mock JSON, and validation result directly to your device.
No signup or email address required. Your input is processed in the browser.