Improve error messages in api

**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 locating the API authentication error-handling entry points. Review the existing error paths and determine which debugging details are missing; this is done when authentication failures consistently produce more descriptive messages and the relevant behavior is covered by the project's checks.

Written by the indexing model from the issue text.