Refactor handlers for better readability

**Problem**
When working with services, 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 no files, tests, or entry points. Start by locating the service handlers and their existing error paths, then review how errors are currently reported; done means the relevant handlers are easier to read and produce more descriptive errors, with tests or checks covering the changed behavior.

Written by the indexing model from the issue text.