Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations declare readOnlyHint=false, openWorldHint=true, destructiveHint=false, and the description adds real side-effect scope: 'The other requests of the user do not change' and the persistence lifecycle 'stays active until the user withdraws it.' Both are behavioral facts not present in the annotations.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.