Consider deprecating old utils API

**Problem**
When working with lib, 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 old utils API under lib and reviewing how its current error handling is exercised. Clarify which API elements should be deprecated, the migration path, and which error cases need detail; done means the deprecation and improved messages are specified and covered by relevant checks.

Written by the indexing model from the issue text.