Improve routes performance

**Problem**
When working with handlers, 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 named. Start by locating the route and handler error paths in the Shell code, then identify how errors are currently reported; done means the relevant failures produce more descriptive messages and are covered by appropriate tests.

Written by the indexing model from the issue text.