Add TypeScript types for helpers

**Problem**
When working with core, 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 helpers and core error-handling entry points named in the issue; no files or tests are specified. Confirm whether the intended outcome is TypeScript types, more detailed errors, or both, then define completion with the maintainer.

Written by the indexing model from the issue text.