Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
The readOnlyHint annotation already declares this as a safe read operation. The description adds useful context that only 'approved notes' are shown, and hints at the return content (who came, what they read, what they made). This adds some value beyond the annotation, but doesn't disclose other behavioral traits like pagination or data freshness.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.