Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Beyond annotations (readOnlyHint=false, idempotentHint=true, destructiveHint=false), the description adds critical context: the tool costs tokens, is not read-only, and requires admin privileges. This transparency about cost and authorization goes well beyond structured fields, with no contradictions to annotations.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.