Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare this is a non-read-only, non-destructive, non-idempotent, closed-world write. The description adds the useful scope constraint that promises/outcomes/rules are out of scope and that the program is private, but it says nothing about duplicate handling (relevant since idempotentHint=false) or required permissions.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.