Add TypeScript types for models

**Problem**
When working with controllers, 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 model definitions and controller error-handling entry points mentioned in the issue. Review how controllers currently report errors and how models are represented, then clarify the expected TypeScript types and message details with the maintainers; done means the requested model types and more descriptive controller errors are covered.

Written by the indexing model from the issue text.