Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations only declare readOnlyHint=false, openWorldHint=true, destructiveHint=false, so the description carries real additional weight: it discloses tier requirement, per-aircraft metering, and nuanced calibration caveats for book_total ('ran wide for large mixed books and narrow for books concentrated in one segment') plus which values are excluded. This is exactly the behavioral context an agent cannot infer from structured fields.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.