Three architectural patterns are presented for integrating A2UI (a declarative UI framework) with MCP Apps to build agentic user interfaces. Pattern 1 (A2UI over MCP) serves structured JSON UI payloads directly from MCP servers using a custom MIME type, supporting both static resource delivery and dynamic tool-call-driven generation. Pattern 2 (MCP Apps in A2UI) embeds MCP Apps as secure iframe components within A2UI surfaces, enabling state synchronization between native and sandboxed components. Pattern 3 (A2UI in MCP Apps) packages the A2UI rendering engine inside the MCP App bundle itself, allowing dynamic AI-driven UIs in legacy or non-A2UI host environments with no host-side changes. Each pattern includes demo applications, sample code, and quick-start guides.
