Add TypeScript types for controllers

**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.

The issue names TypeScript controllers and API error handling but gives no files, tests, or entry points. Start by locating the controller definitions and existing error-handling tests, then determine the expected type coverage and message details. Done means controllers have TypeScript types and API errors provide more descriptive messages.

Written by the indexing model from the issue text.