Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so the bar is lower. The description still adds real context beyond them: the signals are proprietary, backtested over 10 years of NZX data, and flagged with 'validated alpha spreads', which honestly frames the score's provenance and limits.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.