claude-code - 💡(How to fix) Fix tool_use produces thousands of malformed items instead of valid output when schema complexity + prompt size exceeds threshold [1 comments, 2 participants]

The model should either produce valid output conforming to the schema, or fail with an error — not silently produce thousands of malformed objects that technically match the schema's type structure but contain no meaningful content.

TL;DR

To mitigate the issue, simplify the schema by removing large enums, maxLength constraints, and description fields, and instead enforce these constraints in the prompt text or post-processing code.

Guidance

• Identify and simplify complex schemas that may be contributing to the degenerate output mode, focusing on removing large enums and constraints.
• Enforce constraints such as character limits and allowed value lists in the prompt text or post-processing code to maintain data integrity.
• Monitor the combined complexity of the schema and prompt, aiming to stay below the observed threshold of around 14-15K characters.
• Consider reviewing related issues (#22394, #5504, #24599) for additional insights or potential fixes.

Example

No code snippet is provided as the issue does not explicitly mention specific code changes.

Notes

The provided workaround suggests that simplifying the schema and moving constraints to the prompt text or post-processing code can help mitigate the issue, but may not be a permanent solution.

Recommendation

Apply the workaround by simplifying schemas and enforcing constraints in the prompt or post-processing code, as this approach has been confirmed to resolve the issue in production.