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Tool schemas cause 400 errors on strict validators (Codex, Vertex AI) #13737
Description
Built-in tool schemas (like question) break on providers with strict JSON Schema validation — Codex, Vertex AI OpenAI-compatible, SGLang, etc.
The question tool has two problems:
additionalProperties: falseis set butmultipleisn't inrequired, which strict validators reject- Zod
.meta()injects$schemaandrefkeywords that aren't valid in OpenAI function parameter schemas
Error from Codex:
Invalid schema for function 'question': In context=('properties', 'questions',
'items'), 'required' is required to be supplied and to be an array including
every key in properties. Missing 'multiple'.
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github-actions commentedon Feb 15, 2026
This issue appears to be closely related to several existing issues addressing the same root cause - missing 'required' field in tool schemas and invalid Zod meta fields:
All of these stem from the same problem in the schema transformation layer where object-based schemas don't include an explicit 'required' field and Zod's `` metadata isn't being stripped. Consider consolidating these issues or using one as the canonical issue for the fix across all providers.
fix: sanitize tool schemas for strict JSON Schema validators (anomaly…
github-actions commentedon Apr 17, 2026
To stay organized issues are automatically closed after 60 days of no activity. If the issue is still relevant please open a new one.