Building a Cost-Efficient Generative UI Architecture in React Native

In this article, I want to share the architecture we built for Generative UI in the Fonyx mobile application. This system is designed to deliver premium native UI experiences while keeping LLM costs extremely low . Tool Calling + Metadata-Driven Rendering Generative UI (GenUI) is emerging as one of the most powerful patterns for AI-native applications. Instead of returning plain text responses, Large Language Models can dynamically orchestrate real UI components inside applications . However, many early Generative UI systems face serious production challenges: extremely high token costs slow response times hallucinated datasets unpredictable UI outputs In the Fonyx mobile application , we implemented a different architecture designed to deliver premium native UI experiences while keeping LLM costs extremely low . The key idea behind this system is simple: Metadata over Data Instead of generating datasets, the model returns lightweight metadata describing what UI should render , while t