Echo — a voice-first, accessibility-friendly AI shopping assistant (Next.js 15 frontend + Express/MongoDB tool gateway). You shop entirely by talking or typing: search products, add to cart, apply coupons, and place orders. Each action is validated server-side by an LLM-driven tool loop before Echo "speaks" the confirmation. Voice runs on AssemblyAI (live Voice Agent/STT) and ElevenLabs (TTS), with a demo path and browser TTS fallback. The UI uses screen-reader live regions, reduced-motion support, and theme/font controls for accessibility.