Tool Definition Builder

Design tools (function calling) for Claude visually. Describe each parameter, then export the tools array, a ready-to-run Python or TypeScript tool-use loop, or a standalone JSON Schema.

Tools in this set

Tool

NameLetters, digits, underscores and hyphens, up to 64 characters. Use a verb_noun style.Description 184 charsDetailed descriptions matter most: aim for 3–4 sentences covering what, when to use, and what it returns.

Parameters

req

Options

Strict mode (strict: true) Guarantees Claude's tool inputs match your schema exactly. Every object gets additionalProperties: false and all properties become required — optional ones are made nullable (e.g. ["string", "null"]) so Claude can pass null instead of omitting them.Example user message (used in code snippets)

[
  {
    "name": "get_weather",
    "description": "Get the current weather for a city. Use this whenever the user asks about current conditions, temperature or whether to bring an umbrella. Returns temperature, conditions and humidity.",
    "input_schema": {
      "type": "object",
      "properties": {
        "location": {
          "type": "string",
          "description": "City and country, e.g. \"Paris, France\""
        },
        "unit": {
          "type": "string",
          "description": "Temperature unit",
          "enum": [
            "celsius",
            "fahrenheit"
          ],
          "default": "celsius"
        }
      },
      "required": [
        "location"
      ]
    }
  }
]

Checks

✓ Looks good — names are valid and everything is described.