Refactor api 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 file, entry point, or test is named. Start by tracing the config API's current error paths and reviewing any existing error-handling tests; done means the relevant failures produce more descriptive messages and the behavior is covered by tests.

Written by the indexing model from the issue text.