Look up or search members of the US Congress via Library of Congress Congress.gov API. Pass bioguideId (e.g. M001190) to fetch one member (full bio, terms, party history, leadership roles, sponsored + cosponsored legislation counts, official website, address). Or filter by congress + state + district, with currentMember=true to limit to seated members. Bioguide IDs are stable across history and are the canonical Congress-member identifier.