build-mcp-app

To add interactive UI widgets to an MCP server, you register tools with _meta.ui.resourceUri and serve HTML resources that run iframe widget code using the @modelcontextprotocol/ext-apps App. This renders forms, pickers, and dialogs inline in the host chat.

The best way to render confirmation dialogs and pickers in a chat host is serving interactive UI widget resources alongside tool results. This replaces fragile plain-text workflows with explicit selection and structured input components using safe messaging patterns.

Yes, the apps surface App connection model works with iframe sandbox and CSP constraints. It enforces safe messaging patterns and prevents external imports that violate CSP, ensuring the widget runtime remains host-compatible.

To serve widget HTML resources alongside tool results without breaking the wire protocol, you add UI resources via _meta.ui.resourceUri. This keeps tool handlers returning data while the resource serves the HTML for the interactive forms.

Yes, you can use build-mcp-app to display progressive outputs and dashboards in a conversation. It applies to scenarios requiring visual display components and status updates served directly within the chat experience via the ext-apps framework.

Interactive forms need a UI resource because plain-text MCP workflows are fragile and cannot handle inline structured input. Registering _meta.ui.resourceUri serves the HTML widget necessary for the host to render the interactive form correctly.