Refactor lib for better readability

**Problem**
When working with auth, 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 examining the authentication-related code under lib and identify where current error messages are generated. Review the surrounding error-handling flow and existing tests, if any. Done means the relevant authentication failures provide more descriptive messages without changing unrelated behavior.

Written by the indexing model from the issue text.