What's the difference between the two formats?

OpenAI wraps the schema as {type:'function', function:{...parameters}}; Anthropic uses {name, description, input_schema}. The builder outputs the right one.

Add an 'object' parameter, then edit the generated JSON to add nested properties.

Is anything uploaded?

No — the schema is built locally in your browser.

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Function / Tool Schema Builder

Free · No Server

Build OpenAI function-calling or Anthropic tool-use JSON schemas from simple fields.

Function / Tool Schema Builder

Function name

Description

Parameters

required

OpenAI tools[] entry

{
  "type": "function",
  "function": {
    "name": "get_weather",
    "description": "Get the current weather for a location.",
    "parameters": {
      "type": "object",
      "properties": {
        "location": {
          "type": "string",
          "description": "City and state, e.g. Dhaka, BD"
        },
        "unit": {
          "type": "string",
          "description": "celsius or fahrenheit"
        }
      },
      "required": [
        "location"
      ]
    }
  }
}

100% in-browser. Builds a valid JSON-Schema tool/function definition for OpenAI function-calling or Anthropic tool-use. Edit the JSON for nested objects.

What is Function Schema Builder?

The Function / Tool Schema Builder turns a function name, description and a list of parameters into a valid JSON-Schema tool definition for OpenAI function-calling or Anthropic tool-use. It builds the correct wrapper for each provider and updates live in your browser.

How to Use

1
Pick a provider
OpenAI or Anthropic — the wrapper format differs.
2
Define the function
Set the name and description.
3
Add parameters
Add each parameter's name, type, description and required flag, then copy the JSON.

Common Use Cases

Defining tools for function-calling agents
Prototyping LLM tool schemas
Converting an API into a tool definition
Learning the tool-use JSON format

Key Features

OpenAI & Anthropic formats
String/number/boolean/array/object params
Required-field handling
Live JSON output
Copy to clipboard

🔒

100% Private — No Server Required

All processing happens directly in your browser. No data is uploaded, stored, or transmitted to any server.

Frequently Asked Questions

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Last reviewed on June 24, 2026 by the AiTechWorlds Tools Team. All processing runs locally in your browser.

AiTechWorlds

{ "type": "function", "function": { "name": "get_weather", "description": "Get the current weather for a location.", "parameters": { "type": "object", "properties": { "location": { "type": "string", "description": "City and state, e.g. Dhaka, BD" }, "unit": { "type": "string", "description": "celsius or fahrenheit" } }, "required": [ "location" ] } } }