Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already carry readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is covered and the bar is lower. The description adds genuinely useful behavior beyond annotations: the data comes from SEC EDGAR XBRL company facts with no API key, all values are expressed as percentages (including the 0.03 = 0.03% example), include_all_classes changes row cardinality, and the rr: taxonomy coverage caveat is disclosed. Minor gap: no rate-limit or error-shape detail, but this is modest for a read-only lookup.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.