Refactor controllers for better readability

**Problem**
When working with validation, 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 controllers and validation or error-handling entry points in the repository, then inspect how current validation failures are reported. Clarify which messages need more detail before changing behavior; done means validation errors are more descriptive and the existing checks pass.

Written by the indexing model from the issue text.