Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false, and openWorldHint=true. The description adds significant behavioral context: return format (annualized IV in PERCENT, plus min/median/max/percentile), interpretation guidance (IV alone is meaningless without percentile), derivation of expected moves with time scaling warning, and error behavior for unsupported coins. No contradictions with annotations.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.