tool-schema-fixer

tool-schema-fixer is a small Node.js CLI for taking generic JSON Schema or tool parameter schema files and normalizing them into shapes that are friendlier to OpenAI, Anthropic, and Gemini tool-calling flows.

The first release is intentionally conservative. It focuses on a clear set of rules that are practical in real tool schemas, emits a machine-readable or text report, and avoids pretending to fully transpile every JSON Schema feature into every provider's subset.

• Reads a JSON file containing either a plain schema or a common tool wrapper.
• Supports lint for compatibility analysis.
• Supports fix --target openai|anthropic|gemini for normalization.
• Writes the fixed schema to stdout or a file.
• Emits a report describing applied fixes and anything that still needs manual review.

Supported wrapper shapes:

• Plain schema: the file itself is the schema.
• OpenAI-style tool wrapper: {"type":"function","function":{"parameters":{...}}} or {"function":{"parameters":{...}}}
• Generic tool wrapper: {"name":"...","parameters":{...}}
• Anthropic-style tool wrapper: {"name":"...","input_schema":{...}}

Current rules are deliberately explicit:

• Strip provider-unfriendly metadata keywords such as $schema, $id, example, examples, deprecated, readOnly, and writeOnly.
• Normalize nullable and simple null unions:
• openai: collapse to a single concrete type.
• anthropic: convert to JSON Schema type: ["T", "null"].
• gemini: convert to OpenAPI-style nullable: true.
• Normalize simple type: [...] unions:
• null unions are rewritten using the target's preferred nullability form.
• other unions are kept for Anthropic, or rewritten to anyOf for Gemini and most OpenAI nested schemas.
• Close object schemas with additionalProperties: false when they already declare explicit properties.
• For openai, fill required with every declared property t