Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnly, idempotent, non-destructive, closed-world, so the safety profile is covered. The description adds useful behavioral context by enumerating the accepted input dialects (OpenAI `parameters`, MCP `inputSchema`, Anthropic `input_schema`, plain required/optional args) and call shapes, though it says nothing about failure reporting (which the output schema covers).
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.