TokenPad
Building

Function Calling Tool Schema Builder

Write tool definitions as one line each, get valid JSON schema.

One tool per line: name | description | params

103 characters1 lines0 tokensor drop a file

Tool Schema BuilderExact
0Token change
Token change0no change
Input tokens0what you pasted
Output tokens0what you would send
Token cost of this result
Output tokens0
As input$0.00
× 100K requests$0.00

Everything on this page runs in your browser. Nothing you paste is transmitted, because there is no server here to transmit it to.

Result
 

Why the token count is the point

Tool schemas are sent on every request, whether or not a tool is called. A dozen tools with verbose descriptions and nested parameters routinely exceeds a thousand tokens of fixed overhead, and almost no framework shows you that number.

Writing them here means you see the cost as you add each one, which changes what you are willing to include.

The syntax

One tool per line: name, description and parameters separated by pipes. Parameters are comma-separated name:type pairs, and an exclamation mark marks one as required.

The output switches between Anthropic’s input_schema shape and OpenAI’s nested function shape. They are structurally different enough that hand-porting between them is a reliable source of bugs.

Frequently asked questions

How short should a tool description be?
One precise sentence saying when to call it. The model does not need to know how it was implemented, and the schema already states the parameters — describing them again in prose is paid for on every request.
Should every parameter be required?
No, but be deliberate. Optional parameters with defaults and descriptions serialise into a surprising amount of schema, so an optional parameter the model rarely uses is a permanent cost with occasional benefit.

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