Add TypeScript types for helpers

**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 inspecting the helper code under lib and identify which helpers the title refers to, along with their current error paths. Compare existing type declarations and error messages, then run the relevant project checks to confirm the helpers are typed and failures provide the requested debugging context.

Written by the indexing model from the issue text.