For API and webhook specifications

Turn API JSON
into your starting
schema.json.

Skip writing types and nested structures from scratch. Generate an editable schema draft from JSON and save it right away. Start by downloading a file from the preloaded sample.

Paste your JSON to generate a schema ↓

Free. No sign-up or email required. Input is processed on your device.
Your first download uses the sample schema. After editing or generating, it saves the current content.

Draft 2020-12 starting pointEditable required fields and constraintsSave examples and mock data together

SchemaSmith MCP workbench for generating schemas from JSON and validating data — JSON → schema.json

Free, no sign-upNo email address required.

Input uploaded: 0 BJSON is processed in your browser.

4 tools in oneInference, validation, mocks, and repair.

Download in 1 clickSave the sample without preparing input.

JSON SCHEMA WORKBENCH

Paste JSON. Generate a schema.
Download it beside the result.

Replace the JSON on the left and select “Generate schema.” Adjust required fields and constraints on the right, then save using the button below. If you do not have JSON ready, try the preloaded example.

01 JSON data

{
  "id": 1042,
  "name": "Ada",
  "active": true,
  "roles": ["admin", "editor"],
  "profile": {
    "email": "ada@example.com",
    "timezone": "Europe/London"
  }
}

Types and required keys are inferred from the sample. Adjust the generated schema to match your business requirements.

02 Editable JSON Schema

Free, no sign-up, processed on your device. Save the schema on the right as a standalone file.

The sample schema is ready

The generated schema is shown on the right. Save it as schema.json, or replace the sample with your own JSON and generate a new schema.

The bundle includes the schema, input example, mock data, and validation results for both. Any issues requiring mock adjustments are recorded too.

TAKE IT INTO YOUR AI WORKFLOW

Download a local MCP server, too.

Use inference, validation, mock generation, and repair through a local Node.js MCP server. No dependency packages required; it communicates over standard input and output.

Free, no sign-up. Requires Node.js. Review the source and replace the absolute path in the configuration with your saved file's location.

{
  "mcpServers": {
    "schemasmith": {
      "command": "node",
      "args": [
        "/absolute/path/to/schemasmith-mcp.mjs"
      ]
    }
  }
}

FOR API SPECS, WEBHOOKS, AND QA

Spend less time transcribing,
more time reviewing your spec.

Manually identifying types in nested responses. Tracking down integration errors. Get a starting point for these tasks in one screen.

Start your spec review with a draft

Turn a JSON structure into an initial schema. Review types, nesting, and required keys, then edit it to match your actual data specification.

Draft 2020-12 schema declaration
Merge object schemas within arrays
Infer email, URI, and date formats

Find what to fix by its path

Check for type mismatches and missing required fields. Paths such as “$.profile.email” show the location so you can compare it with your source data and make corrections.

type, required, enum, and const
String, number, and array constraints
Local references, composition, and conditionals

Save your QA materials together

Bundle the schema with the input example, mock data, and validation results. Download them for integration checks or sharing with your team.

Choose a standalone schema or JSON bundle
Include mock validation results
No input data sent to a server

Free, no sign-up, processed on your device. Filename: schemasmith-bundle.json

PASTE → REVIEW → SAVE

From your JSON
to a downloadable schema.

Paste a sample response

Put your API JSON or webhook payload on the left. If you do not have one ready, use the preloaded sample to see what the file contains.

Generate and review required fields

Select “Generate schema” to display a draft on the right. Edit required fields, allowed values, and constraints, then check them with “Validate data.”

Download what you need

Choose schema.json for just the specification, or the JSON bundle for QA materials too. Manually edited schemas are preserved when you save.

Free, no sign-up, processed on your device. Review it against your business requirements before production use.

BEFORE YOU DOWNLOAD

What you get.
What the tools can do.

What do I get when I click the first button?

You download a JSON Schema file named schema.json. Your first download contains the schema generated from the preloaded sample. If you switch to your own JSON, an automatically generated schema is updated when you save. Manually edited schemas are preserved. No email address or account is required.

How does the schema differ from the JSON bundle?

schema.json contains only the schema. schemasmith-bundle.json includes the schema, input example, mock data, validation results for both the example and mock, and usage notes. You can also extract the schema field from the bundle and use it as a standalone schema.

Can I download with empty fields?

Yes. If the schema field is empty, a schema is generated from the input JSON. If the input is also empty, the sample is used. When an edited schema exists, saving the standalone schema preserves it. Saving a bundle fills empty input with the sample and records its validation results against the edited schema. Invalid JSON is never silently replaced with the sample.

Is my input data sent anywhere?

JSON, schemas, mock data, and validation results are processed on your device and are not uploaded. Input stays within this tab and resets when you reload. Page-view, CTA-click, and successful-operation tracking does not include your input or generated content. A CTA click does not mean a completed sign-up.

Can I use the generated schema directly in production?

It is a starting point inferred from sample data. It cannot determine business requirements such as required fields, allowed values, or value ranges. Edit and review it, then check it in the validation environment you will actually use.

Which validation keywords are supported?

Supported keywords include type, required, properties, additionalProperties, enum, const, local JSON Pointer references, allOf, anyOf, oneOf, not, if, then, else, string, number, array, and object constraints, uniqueItems, contains, patternProperties, propertyNames, and dependentRequired. This validator does not cover every Draft 2020-12 keyword and does not fetch external references.

Will mock data always match the schema?

Not necessarily. Values are generated from const, default, examples, enum, and types, then validated. Complex patterns or combinations of constraints may require manual adjustments. Issues are recorded on screen and in the JSON bundle.

How do I use the MCP server?

Save schemasmith-mcp.mjs and review its source. Add a configuration to a compatible client to launch it with Node.js, replacing the absolute path with the saved file's location. It provides the same inference, validation, mock generation, and repair functions as the browser tool over standard input and output. A compatible client and client-side configuration are required.

Free, no sign-up, processed on your device. Start by reviewing the sample schema.

Start your next spec review
with schema.json.

Get a draft before you start writing out types and nested structures. Even without your own JSON ready, you can save the sample schema right away.

Free. No sign-up or email required. Input is processed on your device.
After saving, keep generating and validating with your own JSON.

API spec draftsWebhook checksQA mock dataLocal MCP