Update services documentation

**Problem**
When working with core, the error messages could be more descriptive.

**Suggestion**
Improve error handling and add detailed error messages.

**Context**
This would help with debugging and maintenance.

No files, tests, or entry points are named. Start by locating the core services documentation and the error-handling paths it describes, then determine which messages are currently too vague. Done means the relevant service documentation and error messages provide the detailed debugging context requested.

Written by the indexing model from the issue text.