Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint=true, and the description adds real context beyond that: the level is derived from role grants in force in the database 'exactly as the gateway sees them', and warnings flag concrete unsafe states (a table without RLS open to visitors, a grant lacking USAGE on its schema). It stops short of pagination, volume, or failure behavior.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.