Refactor validation for better readability

**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 route-handling validation and existing error-message tests in the repository, since the issue names no files or entry points. Read the current validation flow and determine which route failures need clearer messages; done means the handling is easier to read and detailed errors are covered by tests.

Written by the indexing model from the issue text.