Update controllers documentation

**Problem**
When working with routes, 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 route-handling entry points mentioned in the issue, then determine whether the requested work is documentation-only or also changes error handling. Done should mean the scope is resolved and the relevant route errors have more descriptive messages, with corresponding documentation updated.

Written by the indexing model from the issue text.