Optimize validation for large datasets

**Problem**
When working with lib, the error messages could be more descriptive.

**Suggestion**
Improve error handling and add detailed error messages.

**Context**
This would help with debugging and maintenance.

Start by locating the validation logic under lib and trace how its current errors are produced for large datasets. Clarify which validation failures need more detail, then verify that the resulting messages improve debugging without changing validation behavior.

Written by the indexing model from the issue text.