# Convert Tool-Calling Schemas Between Providers

> Move a function definition between OpenAI, Anthropic, Gemini, MCP and bare JSON Schema — or emit it as a TypeScript type or Zod schema.

This converter translates a tool definition between the OpenAI chat-completions and responses shapes, Anthropic's Messages API, Gemini function declarations, MCP tool definitions and bare JSON Schema, and can emit the same schema as a TypeScript interface or a Zod schema. It also applies strict mode correctly — recursively adding additionalProperties: false and marking every property required.

**URL:** https://convertto.tech/t/tool-schema-converter
**Category:** AI & LLM Tools (https://convertto.tech/c/ai-tools)
**Privacy:** Runs entirely in the browser; no upload
**Cost:** Free, no sign-up
**Last updated:** 2026-08-01

## Key facts

- **Privacy:** Runs entirely in your browser — nothing is uploaded
- **Cost:** Free, unlimited, no sign-up

## How to use

1. Enter or paste your tool definition.
2. Choose the from.
3. Choose the to.
4. Turn "Strict mode" on or off as needed.
5. Press Run, then download the result when it is ready.

## FAQ

### What does strict mode actually change?

It guarantees the arguments the model produces validate against your schema exactly. In exchange, the schema must set additionalProperties: false and list every property as required at every level. An optional field is expressed as a union with null, not by leaving it out of `required` — this tool applies that transformation recursively.

### Why does Gemini need different types?

Gemini accepts an OpenAPI 3.0 subset rather than JSON Schema: type names are upper-case ("STRING", "OBJECT") and several keywords, including additionalProperties, are rejected outright. The converter upper-cases and strips them for you.

## Sources

- [JSON Schema specification](https://json-schema.org/) — JSON Schema
- [Model Context Protocol — tools](https://modelcontextprotocol.io/docs/concepts/tools) — MCP

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