Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full burden. It discloses that the tool writes the current scene to disk, which is the key side effect, but it does not explicitly mention that an existing file will be overwritten, whether changes are reversible, or what happens if no scene is open. The Ctrl+S analogy partially covers standard overwrite behavior.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.