Look up entities registered to do business with the US federal government in SAM.gov. Search by ueiSAM (12-char Unique Entity ID), cageCode, or legalBusinessName (provide at least one); page with limit (1-100). Returns each entity with its UEI, CAGE code, legal and DBA name, SAM registration status and dates (registration, expiration, last update), purpose of registration, an active-exclusion flag, physical address, and business types — plus a total match count. Data: SAM.gov entity management, free and public-domain (registration core data; sensitive FOUO sections are not returned). The canonical federal counterparty identity key — pair with /api/gov/exclusions (debarment) and /api/law/sanctions-check (OFAC) for full counterparty due diligence.