Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full behavioral burden and does well: it discloses that output is purely descriptive, that every result includes window_days, match count, and per-population base rates, and it explains the researcher-degrees-of-freedom rationale for not labeling results as 'correlation'. This goes well beyond a bare read/analysis disclosure. It does not state computational complexity, refresh behavior, or permission requirements, which keeps it short of a 5.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.