Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Beyond the annotations (readOnlyHint=false, destructiveHint=false, idempotentHint=true), the description explains the blast radius (all Instagram accounts at once, no approval gate), the runtime effect on in-flight state ("stops answering new people; conversations already under way finish"), and that nothing is deleted. It also confirms reversibility, which the annotations alone cannot convey.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.