Function Calling Designer - Free Online Tool | PivaBox

Visually design function calling / tool use schemas — export to OpenAI, Anthropic, or Generic JSON Schema format

How to Use Function Calling Designer

1. Enter a function name and description, then click + Add Parameter to define each input parameter with its name, type, and description
2. For object-type parameters, add sub-properties; for enum types, specify the allowed values (comma-separated)
3. Select your target format (OpenAI, Anthropic, or Generic JSON Schema) and click Copy to copy the generated schema to your clipboard

Frequently Asked Questions

Is Function Calling Designer free?

Yes, PivaBox Function Calling Designer is completely free to use. All processing runs locally in your browser — no data is sent to any server.

What output formats are supported?

The tool supports three formats: OpenAI function calling format (with <code>type: "function"</code> wrapper), Anthropic tool use format (with <code>input_schema</code> key), and Generic JSON Schema format without platform-specific wrappers.

Can I edit an existing schema?

Yes! Paste any existing function schema JSON into the Import field and click Import. The tool will parse it and populate the form fields so you can modify and re-export it in any format.