Tool contract check · local only
What changed in this tool?
Find the field. Review the change. Check your examples before taking it back to your code.
No tool definition? Diagnose a Codex error instead →Your result belongs here
Two definitions. Recorded differences.
Compare the same tool before and after a change. Nothing runs until you choose Compare versions.
- Definition
- Not checked
- Argument examples
- Not supplied
- Runtime
- Not tested
This is a static preflight, not a connection test or a promise that the model will call your tool.
What this check can establish
Choose the request format you actually use. Both targets here explicitly check OpenAI function tools with strict: true; the checker does not infer either API’s behavior when strict is omitted.
Checks and examples
Covered schema shapes include objects, arrays, scalar types, nullable types, enum, anyOf and documented numeric, array, pattern and format constraints. Each object is checked for closed extra properties and required fields. Argument examples are evaluated locally with a JSON Schema interpreter.
Changes need your decision
Requiring a previously optional field or refusing extra fields changes valid input. Proposals start unselected. Nothing silently adds null, drops an enum, removes an unsupported constraint, edits your original, or modifies your server.
Explicit limits
One tool, 32 KiB definition, 16 KiB of examples and a bounded worker deadline. References, other dialects, fine-tuned models and unlisted keywords are outside this first profile. Incomplete coverage never becomes a complete check. Actual model selection, authentication, execution and output behavior remain untested.
Compare versions, not guessed compatibility
Compare two complete definitions of the same function tool within the selected API format. Confirm identity yourself; names alone do not establish the same tool. See added, removed and changed field values, plus the same argument examples evaluated on both sides. Formatting, object-key order and genuine unique schema-required order are ignored; other array order is preserved. No differences or unchanged examples do not prove equivalent behavior. No definitions are rewritten in comparison mode. Local reports contain diff values, not complete definitions or raw argument examples; review them before sharing.
Comparison method checked 2026-09-07: Object and required semantics · Ordered arrays. Whole MCP inventories and cross-format comparison are not supported.
Source rules checked 2026-09-05: OpenAI strict function calling · Supported schema subset · Interpreter license.
Already connected but the tool is missing? Continue with the Codex diagnostic. Need to share findings? The result includes a maintainer brief without your full definition or argument values.