Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already cover the safety profile (readOnlyHint, idempotentHint, destructiveHint=false), and the description adds real substance: it explains the detection method (front-run + back-run in surrounding transactions) and scopes the read to "recent" history. It stops short of stating scanning depth/window limits or expected latency, so it is strong rather than exhaustive.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.