Update services documentation

**Problem**
When working with store, 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 services and store but no files or tests. First locate the store service and inspect its current error paths; confirm whether the requested change is code, documentation, or both. Done means the intended error cases produce descriptive messages and the services documentation reflects the agreed behavior.

Written by the indexing model from the issue text.