Unbound employees first, because they are the rows an administrator has something to do about. unmatched_members is the firm's own members nobody is bound to, so it is visible who is missing. For a system each member signs in to it is the same table, read-only: the people who have signed in, each bound to the member who did (bound_by is sign_in), and unmatched_members is the members who have not signed in yet. Its write stays a 404 there. A firm connected to a system this service carries no adapter for answers the not-available 422.

Operator mount: an operator acting for the firm named in the path, as its oldest active admin, else its oldest active billing member; X-Six-Minute-Acting-As names them. 404 for no such firm, 409 urn:six-minute:problem:no-acting-member for one with neither.