Add TypeScript types for utils

**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 lib directory and locating the utils entry points mentioned by the issue. Determine which utility APIs need TypeScript types and which error paths need more descriptive messages; done requires an agreed scope plus tests or documented checks for the resulting types and errors.

Written by the indexing model from the issue text.