Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint, idempotentHint, and destructiveHint, so the safety profile is covered. The description adds meaningful context by enumerating the specific analysis dimensions (minified+gzipped size, tree-shakeability, dependencies, ESM/CJS), which informs the agent about the tool's output focus. It does not describe error behavior or return format, but that is acceptable given the output schema exists.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.