Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint=true and destructiveHint=false, so the tool is known to be safe. The description adds 'any watchlist you own or follow,' which clarifies scope but does not disclose additional behavioral traits like auth requirements or rate limits. It meets the baseline with annotations but adds little extra.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.