Add TypeScript types for utils

**Problem**
When working with routes, the error messages could be more descriptive.

**Suggestion**
Improve error handling and add detailed error messages.

**Context**
This would help with debugging and maintenance.

No file, test, or entry point is named. Start by locating the route utilities and existing TypeScript type definitions, then clarify whether the intended outcome is adding utility types, improving route error messages, or both; done should be verified by the project's relevant checks and clearly defined error behavior.

Written by the indexing model from the issue text.