Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations declare readOnlyHint=false and destructiveHint=false, so the agent already knows this is a non-destructive mutation. The description adds the useful reset behavior (empty title → file name or "untitled N"), but says nothing about invalid tab_id handling or other side effects, so it adds some value without fully describing behavior.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.