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JSON to Function Calling Schema Generator

Turn an example argument object into a provider-targeted tool declaration for OpenAI, Claude or Gemini. Review the generated wrapper and parameter schema against the provider’s current official API before integration.

Direct answer

Function calling lets a model choose a declared tool and produce structured arguments for your application to execute. Providers use related but different wrappers, so select the target and validate the output against the current SDK/API.

Choose the provider, generate the declaration and validate it before adding the tool to production code.

1

Input JSON

Example JSON loaded.
Valid JSON11 lines · 232 bytes
2

Function Calling Schema

Target
1{"name":"getWeather","description":"Get the current weather for a location","parameters":{"type":"object","properties":{"name":{"type":"string","description":"name","default":"getWeather"},"description":{"type":"string","description":"description","default":"Get the current weather for a location"},"location":{"type":"object","properties":{"type":{"type":"string","description":"type","default":"string"},"description":{"type":"string","description":"description","default":"City name, e.g. Tokyo"}},"required":["type","description"],"additionalProperties":false,"description":"location object"},"unit":{"type":"string","description":"unit","default":"celsius"},"includeforecast":{"type":"boolean","description":"include forecast","default":true},"days":{"type":"integer","description":"days","default":3}},"required":["name","description","location","unit","includeforecast","days"],"additionalProperties":false}}

How to use it

  1. Paste/upload a representative JSON argument object or fetch a supported public sample.
  2. Set function name/description, naming style, required fields, descriptions, enum inference and defaults; choose the provider target.
  3. Review raw/formatted/preview and usage-example views, then compare the output with current official provider documentation before copying it into code.

Key features and settings

  • Targets currently shown: OpenAI, Claude and Gemini.
  • Function name, description and parameter naming controls.
  • Required, description, enum and default inference.
  • Raw, formatted, tree/preview and usage-example export views.

Supported input and output

Input: a JSON object example, a supported public URL. Output: a provider-targeted tool/function declaration, a usage example.

Use cases

  • Bootstrap an LLM tool declaration from an existing request payload.
  • Compare provider wrappers for the same argument schema.
  • Document the proposed tool parameters before SDK integration.

Which workflow should you choose?

Use JSON to Function Calling Schema Generator for: Targets currently shown: OpenAI, Claude and Gemini. Use JSON to JSON Schema Generator for: Draft selection from legacy drafts through 2020-12 in the current UI.

Privacy and data path

In the current implementation, pasted/uploaded content is processed in the browser, while “Extract from URL” uses a server-side proxy to fetch the source.

Limits and troubleshooting

  • Provider product labels and API surfaces change, so compare generated wrappers with current official documentation.
  • Generated defaults/enums and “required” fields can overconstrain tool calls when inferred from only one example.
  • There is no universal size promise; large-input performance depends on browser memory and device capability.

FAQ

Will one generated schema work unchanged with every provider?

No. The parameter model is related, but wrappers, supported keywords and SDK shapes differ. Choose a target and verify the result against the provider’s current official documentation.

Is my data uploaded to a server?

In the current implementation, pasted/uploaded content is processed in the browser, while “Extract from URL” uses a server-side proxy to fetch the source.

What are the file or data limits?

There is no universal size promise; large-input performance depends on browser memory and device capability.

Does it work on mobile?

The page is web-based and may work in a modern mobile browser, but file-picker behavior, memory and cross-device compatibility are not verified for every device. Use a desktop browser for large or complex inputs.

Which workflow should you choose?

Use JSON to Function Calling Schema Generator for: Targets currently shown: OpenAI, Claude and Gemini. Use JSON to JSON Schema Generator for: Draft selection from legacy drafts through 2020-12 in the current UI.

Related tools

JSON to JSON Schema GeneratorGenerate standalone JSON Schema with explicit dialect control.JSON to Zod Schema GeneratorGenerate a starting point for runtime validation in TypeScript.JSON to TypeScript GeneratorGenerate compile-time interfaces/types from a JSON payload.

Choose the provider, generate the declaration and validate it before adding the tool to production code.