Refactor auth for better readability

**Problem**
When working with types, 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 authentication code and its existing type-related error handling, then review how current messages are produced; done means the relevant errors are more descriptive and the existing checks still pass.

Written by the indexing model from the issue text.