Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations provided, so description carries the behavioral burden. It transparently states the tool is a calculation returning a structured object with weeks, months_approx, and working_days. No side effects are mentioned, which is appropriate for a pure calculation tool.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.