Update data documentation

**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 does not name any files, tests, entry points, services, or specific error cases. First clarify which services and failure paths are in scope, then locate their Shell entry points and existing error handling. Done should mean that the agreed cases produce detailed, useful messages and have coverage or reproducible checks.

Written by the indexing model from the issue text.