Optimize validation for large datasets

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

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

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

The issue names no files, tests, or entry points. Start by locating validation and type-error handling in the CLI, then clarify which large-dataset behavior and message details are expected. Done means the validation remains usable for large datasets and produces the agreed descriptive errors, backed by tests.

Written by the indexing model from the issue text.