Optimize auth for large datasets

**Problem**
When working with api, 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 names no files or tests. Start by locating the API authentication error-handling entry points and review the current messages and failure cases; done means the affected errors provide detailed, useful messages for debugging and maintenance.

Written by the indexing model from the issue text.