Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations only flag destructive/openWorld; the description goes well beyond them by disclosing re-grading, replacement of matching rules, plan-space-dependent activation, queued public-network searches and ranking checks, alert synchronization, case-only no-ops, and duplicate failure. For a destructive mutation, this is exactly the side-effect detail an agent needs.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.