Refactor types 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.

The issue does not name a file, test, or entry point. Start by locating the authentication-related error handling and tracing where its messages are produced. Before changing anything, clarify which errors and message details are in scope; done means the agreed errors provide more descriptive messages and the existing behavior remains understood.

Written by the indexing model from the issue text.