Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already establish readOnlyHint, idempotentHint, destructiveHint=false, and openWorldHint=false. The description adds useful behavioral context beyond that: quote.maxCharge is the maximum run cost, quote.needsConfirmation triggers above $0.10, and the tool is free.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.