Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint/destructiveHint/openWorldHint, so the safety profile is covered. The description adds genuinely non-obvious behavior beyond them: entitlement-gated catalog results, silent empty results for unsubscribed accounts, and that browsing cannot initiate an Apple subscription.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.