Consider deprecating old core API

**Problem**
When working with utils, 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 or tests are named. Start by locating the utils code, the core API referenced in the title, and existing error-handling paths; clarify which API is being deprecated and which errors need richer messages. Done should be defined by the maintainer as a specific deprecation scope plus descriptive errors and corresponding coverage.

Written by the indexing model from the issue text.