Refactor data for better readability

**Problem**
When working with config, 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 config handling and current error-message paths, then determine which cases need more detail; done means the relevant config errors are clearer and the existing checks still pass.

Written by the indexing model from the issue text.