Update core 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 route-handling code and its existing error paths. Review how route failures are currently reported and identify the cases that need more descriptive messages. Done means route errors provide clearer debugging context and the relevant checks or tests pass.

Written by the indexing model from the issue text.