Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations declare readOnlyHint=false and destructiveHint=false, so the write/safe profile is carried by structured data. The description adds nothing beyond that — no side effects, no name-collision behavior, no sync implications for a snippet that may be pushed to nodes.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.