Add TypeScript types for utils

**Problem**
When working with api, 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 utils code and the API error-handling entry points; the issue names no files or tests. Review how current errors are created and reported, then confirm the expected TypeScript types and more detailed messages with the maintainers. Done means the relevant utility types exist and API errors provide the agreed descriptive details.

Written by the indexing model from the issue text.