Mercor is a profitable Series C AI data company that connects millions of domain experts with frontier AI labs and Fortune 500 enterprises. Experts get paid to train models and to "capture how their best people actually work," which Mercor then turns into AI agents. Its APEX benchmark family measures how well AI performs real professional tasks. In short: Mercor is the human-expertise layer under frontier models and enterprise AI agents, plus the yardstick that grades them.