Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Adds essential behavior beyond the readOnly/non-destructive annotations: the value is never returned, value_preview is only a non-sensitive hint such as trailing characters, and secret values cannot be set through this assistant. These are exactly the constraints an agent needs to avoid misusing the tool.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.