System Design — Designing Intelligent UIs as MCP Client

MCP (Model Context Protocol) enables a new architectural pattern where the UI acts as an intelligent orchestration layer rather than a thin presentation layer. An MCP Client UI can discover backend capabilities at runtime, understand tool schemas, invoke tools dynamically based on LLM reasoning, and chain multi-step workflows without hardcoded API calls. The recommended architecture includes an MCP Client SDK, a Gateway MCP federation layer, and domain-specific MCP Servers. Key scaling considerations cover tool metadata management, multi-tenant isolation, horizontal gateway scaling, and latency optimization through caching and parallel tool execution. Real-world examples include AI-powered IDEs like Cline and Kiro, and Figma's MCP server integration with agents like Cursor and Windsurf.