Handle edge cases in monitoring

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

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

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

Start by locating the monitoring-related code under lib and reviewing its existing error paths and messages. Identify the edge cases covered by the issue, then verify that failures produce detailed, useful messages and that the relevant checks still pass; no specific test file is named in the issue.

Written by the indexing model from the issue text.