What does strict mode change?

It removes $schema, $id and title, sets additionalProperties: false on every object, and lists all properties as required — the conditions OpenAI strict structured outputs require.

Why must every property be required?

OpenAI strict mode does not support optional properties; the usual workaround is to make the field required but allow null in its type.

Does it validate my schema?

It parses the JSON and reports syntax errors. For deeper validation use the MCP Tool Schema Validator or Structured Output Validator.

Can I use the output with MCP servers?

Yes — pick the MCP target and the schema is emitted under inputSchema, the key MCP clients expect.

Does it work offline and on mobile?

Yes. Once the page has loaded it keeps working without a network connection, and the layout is responsive so it stays usable on phones and tablets.

JSON Schema to AI Tool Schema

Wrap any JSON Schema into a ready-to-use function-calling tool.

Works Offline

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No API

Tool name

Description

Target

Strict mode

JSON Schema

AI tool schema

{
  "type": "function",
  "function": {
    "name": "search_docs",
    "description": "Search the documentation index.",
    "parameters": {
      "type": "object",
      "properties": {
        "query": {
          "type": "string",
          "description": "Search query"
        },
        "limit": {
          "type": "integer",
          "minimum": 1,
          "maximum": 50
        }
      },
      "required": [
        "query"
      ],
      "additionalProperties": false
    },
    "strict": true
  }
}

About the JSON Schema to AI Tool Schema

Paste a plain JSON Schema, add a tool name and description, and export a valid OpenAI, Anthropic, Gemini or MCP tool definition. Strict mode strips unsupported keywords, forces additionalProperties: false and fills the required array so structured outputs validate first time.

Examples

Search schema

{ "type": "object", "properties": { "query": { "type": "string" } } }

Output

OpenAI tool with strict: true

Keyboard shortcuts

Copy the main outputCtrl / ⌘ + Shift + C
Download the resultCtrl / ⌘ + S
Share this toolCtrl / ⌘ + Shift + S
Reset the inputsAlt + R
Open the tool search paletteCtrl / ⌘ + K

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Frequently asked questions

Version 1.0.0 · Updated 2026-08-15 · Runs entirely in your browser