Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description fully carries the behavioral burden. It discloses that the operation mutates a property and returns the new value, but omits side effects, error handling (e.g., invalid property names), permissions, or reversibility. For a mutation tool, this is minimal disclosure.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.