Refactor controllers for better readability

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

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

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

No files, tests, or entry points are identified. Start by locating the controllers and model-related error handling, then determine which messages need more detail and how the improved error handling can be verified for clearer debugging and maintenance.

Written by the indexing model from the issue text.