Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the burden of behavioral disclosure. It usefully states that the tool calculates tip, handles tax inclusion, and produces a per-guest split. However, it does not clarify whether the tip is computed pre-tax or post-tax, what the returned itemized split looks like, or how the default values behave, which is meaningful ambiguity for a financial 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.