Grok 4.1 Review: xAI's Post-Training Leap — #1 on EQ-Bench, 65% Fewer Hallucinations, and the Agent Tools API

Grok 4.1 (November 17, 2025) is xAI's refined post-training update to Grok 4: #1 on EQ-Bench3 (1,586 Elo), 65% hallucination reduction (12.09% → 4.22%), LMArena Elo 1,483 (briefly #1), and the Agent Tools API with server-side managed tools. Grok 4.1 Fast offers 2M context at $0.20/$0.50 per million tokens. Rating: 4/5.