Tool schema generatorGenerators

Function calling schema. One tool, five formats.

Name the tool, describe it and add parameters with a type and a required flag. Get the JSON each API expects: Anthropic tools, OpenAI Chat Completions, OpenAI Responses, Gemini function declarations or an MCP tool. Arrays hold strings only.

Cost to you

Free

Runs in your browser. No signup, no API call, no limit per hour.

browser
runs in
none
API calls
none
account

Use it now

Use the LLM tool schema generator here

It runs in your browser. Nothing you type is sent anywhere, there is no signup and no limit.

Loading the tool.

Run it from your agent

Copy one prompt, give it to your agent.

Fill in the placeholder, paste it, and the agent runs the same job with current data on your looot account and shows the cost.

  • You give it: a tool name, a description and parameters with types.
  • Billed per call, nothing while your agent is idle.
  • The agent shows the price before it calls.
Prompt: LLM tool schema generator
Use looot to give my agent a tool for [job]. 1. Set up https://looot.ai/skill.md. 2. Search the looot catalog for an endpoint that does the job and read its input parameters. 3. Write a tool definition in the [Anthropic or OpenAI] format whose parameters match the endpoint's required inputs. 4. Return the JSON and one example call.

Give this to your agent
Setup command
set up looot - https://looot.ai/skill.md

What comes back

What your agent gets from function calling schema generator

Field names as the providers return them. The exact set varies by endpoint, and your agent reads it from the catalog.

  • tool definition JSON per format
  • JSON Schema of the parameters
  • OpenAI strict mode variant
  • download as .json

Use it for

What people do with function calling schema generator

  • Give an agent a tool

    Write the definition once and paste it into your tools array.

  • Switch providers

    Move a tool from one API to another without rewriting the JSON by hand.

  • Strict mode

    Get the OpenAI strict variant with every field required and nulls for optional ones.

  • Build an MCP server

    Copy the inputSchema your tools/list handler returns.

Set up once

Three steps. Your agent does the rest.

Keep going

More free tools

FAQ

Questions about function calling schema generator

A JSON description of a tool: its name, what it does and a JSON Schema of its parameters. The model reads it and returns arguments that match.

Anthropic puts the schema in input_schema next to name and description. OpenAI Chat Completions wraps them in a function object with type function. The Responses API keeps them flat.

Every property must be listed as required and additionalProperties must be false. An optional field becomes a union with null, so the model can leave it empty.

Pick MCP. You get name, description and inputSchema, the shape a server returns from tools/list.

Not in this generator. Arrays hold strings and there are no nested objects. Edit the JSON after you copy it for those.

The model decides when to call a tool from its description. Say what it does and when to use it.

Yes. It runs in your browser with no account and no limit.
For agents
tool
LLM tool schema generator
category
Generators
input
A tool name, a description and parameters with types
output
tool definition JSON per format, JSON Schema of the parameters, OpenAI strict mode variant, download as .json
price
per call, read live from the catalog on the web page
web tool
runs in the visitor's browser, no API call, free and unlimited
schedule
on demand
setup
https://looot.ai/skill.md
llms.txt
https://looot.ai/llms.txt
updated
2026-10-14
markdown /free-tools/llm-tool-schema-generator.md

Run function calling schema generator from your own agent.

Start your workspace, top up, and paste the prompt into the agent you already use. It runs the job with live data and shows the cost first.

Start your workspace See all free tools