Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare the tool as read-only, idempotent, and non-destructive. The description adds valuable behavioral details: it returns MCP URL, mcpVerified, last-verified timestamp (when available), and probed tool list read from endpoint (not maker-supplied tags). This enriches the agent's understanding beyond the structured annotations.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.