Update auth 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.

The issue mentions authentication, routes, and error messages but names no files, tests, or entry points. Start by locating the route and auth handling code, then clarify which messages and documentation need changing; done means the requested auth documentation is updated and route errors are more descriptive.

Written by the indexing model from the issue text.