JSON Schema and tool validator

Validate JSON Schema and OpenAI- or Anthropic-style function definitions locally, with clear structural errors before you call an LLM API.

How to use this tool

Paste a JSON Schema or a JSON tool definition into the editor.
Select Validate JSON.
Fix any inline structural errors before sending the definition to a model API.

Worked example: Example: a function definition with a string name and an object-shaped parameters field passes the basic local validation.

JSON Schema or tool definition

{
  "type": "function",
  "function": {
    "name": "get_weather",
    "description": "Get current weather for a city.",
    "parameters": {
      "type": "object",
      "properties": { "city": { "type": "string" } },
      "required": ["city"]
    }
  }
}

Valid structure

Recognized as a openai tool.

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