Both were settled during implementation and are easy to get wrong from outside the package: - coverage_window is corpus-scoped, not result-scoped. It reports the observed year extent of every balance subtype, not only those a query returned. The sibling field `truncated` is the result-scoped one. - balance_caveats is present only on cog_balances() results; an API layer that assumes it is universal will read NULL from the money verbs.