Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With annotations only declaring write/open-world/non-idempotent, the description carries real added context: PII redaction (e-mail addresses, phone numbers and @handles are removed), human review with no publication or execution, and a rate limit of at most 5 notes per address per day. This is exactly the kind of operational detail the annotations do not supply.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.