Function getUiCapability

getUiCapability(
    clientCapabilities:
        | {
            elicitation?: {
                form?: { applyDefaults?: boolean; [key: string]: unknown };
                url?: object;
                [key: string]: unknown;
            };
            experimental?: { [key: string]: object };
            roots?: { listChanged?: boolean };
            sampling?: { context?: object; tools?: object };
            tasks?: {
                cancel?: object;
                list?: object;
                requests?: {
                    elicitation?: { create?: object; [key: string]: unknown };
                    sampling?: { createMessage?: object; [key: string]: unknown };
                    [key: string]: unknown;
                };
                [key: string]: unknown;
            };
        } & { extensions?: Record<string, unknown> }
        | null
        | undefined,
): McpUiClientCapabilities | undefined
Get MCP Apps capability settings from client capabilities.

This helper retrieves the capability object from the extensions field where MCP Apps advertises its support.

Note: The clientCapabilities parameter extends the SDK's ClientCapabilities type with an extensions field (pending SEP-1724). Once extensions is added to the SDK, this can use ClientCapabilities directly.
Parameters
- clientCapabilities:
      | {
          elicitation?: {
              form?: { applyDefaults?: boolean; [key: string]: unknown };
              url?: object;
              [key: string]: unknown;
          };
          experimental?: { [key: string]: object };
          roots?: { listChanged?: boolean };
          sampling?: { context?: object; tools?: object };
          tasks?: {
              cancel?: object;
              list?: object;
              requests?: {
                  elicitation?: { create?: object; [key: string]: unknown };
                  sampling?: { createMessage?: object; [key: string]: unknown };
                  [key: string]: unknown;
              };
              [key: string]: unknown;
          };
      } & { extensions?: Record<string, unknown> }
      | null
      | undefined
  The client capabilities from the initialize response
Returns McpUiClientCapabilities | undefined
The MCP Apps capability settings, or undefined if not supported
Example: Check for MCP Apps support in server initialization
```
import { getUiCapability, RESOURCE_MIME_TYPE, registerAppTool } from "@modelcontextprotocol/ext-apps/server";

server.oninitialized = ({ clientCapabilities }) => {
  const uiCap = getUiCapability(clientCapabilities);
  if (uiCap?.mimeTypes?.includes(RESOURCE_MIME_TYPE)) {
    registerAppTool(server, "weather", {
      description: "Get weather with interactive dashboard",
      _meta: { ui: { resourceUri: "ui://weather/dashboard" } },
    }, weatherHandler);
  } else {
    // Register text-only fallback
    server.registerTool("weather", {
      description: "Get weather as text",
    }, textWeatherHandler);
  }
};
```
- Defined in src/server/index.ts:362

Function getUiCapability

Parameters

Returns McpUiClientCapabilities | undefined

Example: Check for MCP Apps support in server initialization

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