Update parsers documentation

**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 parsers documentation and the auth-related error handling referenced in the issue. Clarify which parser pages and error cases are in scope before making changes. Done means the selected documentation is updated and the relevant auth errors provide more descriptive messages.

Written by the indexing model from the issue text.