Use mcp-ui when an MCP server needs to return more than plain text or JSON and the operator must expose a reviewable interactive surface beside tool results. The workflow is to install the server and client SDKs, create a UI resource with createUIResource, register the resource handler, link the tool through _meta.ui.resourceUri, and test rendering in an MCP Apps-compatible host or legacy MCP-UI host. Invoke this instead of normal SDK usage when a tool result needs a form, dashboard, confirmation panel, or guided interaction that remains tied to the MCP resource contract. The operator should validate the resource URI, MIME type, sandbox behavior, tool input, tool result, and message handlers before exposing the surface to users. Document the host compatibility and fallback behavior for clients that cannot render apps. The scope boundary is UI resource creation and host rendering for a specific MCP tool. It is not a broad front-end framework, design system, or generic MCP server listing.