Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the burden of behavioral disclosure. 'Requires Ninja Forms plugin' is a useful dependency disclosure, and 'List' implies read-only enumeration. It does not state what happens if the plugin is missing or describe the returned data, but the basic behavior for a simple list operation is conveyed.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.