Consider deprecating old api API

**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.

The issue names no file, entry point, or test. First clarify which config API is considered old and locate its error-handling path; done should include an agreed deprecation scope and more descriptive configuration errors, backed by the relevant tests.

Written by the indexing model from the issue text.