Add TypeScript types for utils

**Problem**
When working with models, 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 issue does not name a utility file, model, entry point, or test, and its title conflicts with the body. Start by locating the utilities and model error-handling code, then clarify whether the goal is TypeScript type definitions or more descriptive errors before defining completion criteria and tests.

Written by the indexing model from the issue text.