Add TypeScript types for parsers

**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.

The title asks for TypeScript types for parsers, while the body asks for more descriptive errors in utils. No files, tests, or entry points are named, so first clarify which scope is intended and locate the relevant parser or utility code; done should be defined with concrete type or error-message expectations and verification steps.

Written by the indexing model from the issue text.