MCP Apps Capability Detection

import { getUiCapability, EXTENSION_ID, RESOURCE_MIME_TYPE } from "@modelcontextprotocol/ext-apps/server";

function getUiCapability(
  clientCapabilities: ClientCapabilities | null | undefined,
): McpUiClientCapabilities | undefined

import {
  getUiCapability,
  registerAppTool,
  RESOURCE_MIME_TYPE,
} from "@modelcontextprotocol/ext-apps/server";

server.server.oninitialized = () => {
  const clientCapabilities = server.server.getClientCapabilities();
  const uiCap = getUiCapability(clientCapabilities);

  if (uiCap?.mimeTypes?.includes(RESOURCE_MIME_TYPE)) {
    // Host supports MCP Apps — register tool with UI
    registerAppTool(
      server,
      "weather",
      {
        description: "Get weather with interactive dashboard",
        _meta: { ui: { resourceUri: "ui://weather/dashboard" } },
      },
      weatherHandler,
    );
  } else {
    // Host does not support MCP Apps — register text-only fallback
    server.registerTool(
      "weather",
      { description: "Get weather information" },
      textWeatherHandler,
    );
  }
};

const EXTENSION_ID = "io.modelcontextprotocol/ui";