Add TypeScript types for api

**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.

First clarify whether the task is to add TypeScript types for the API or to improve controller error messages, since the title and body describe different work. Then locate the API and controller entry points mentioned in the issue, identify existing tests if present, and define completion as the selected scope being covered consistently.

Written by the indexing model from the issue text.