Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations provide readOnlyHint=true and destructiveHint=false, so the read-only nature is clear. The description adds 'in full' but no further behavioral details (e.g., response size, errors). Annotations carry most of the burden; description is adequate but minimal.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.