MCP Apps
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    Function getUiCapability

    • Get MCP Apps capability settings from client capabilities.

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

      Parameters

      • clientCapabilities:
            | {
                elicitation?: {
                    form?: {
                        applyDefaults?: boolean;
                        [key: string]: | string
                        | number
                        | boolean
                        | {
                            [key: string]: string | number | boolean | { [x: string]: string | number | boolean | ... | (string | number | boolean | ... | (string | number | boolean | ... | (string | number | boolean | ... | (string | ... 4 more ... | null)[] | null)[] | null)[] | null)[] | null; } | (string | ... 4 more ... | null)[] | null;
                        }
                        | (
                            string | number | boolean | { [x: string]: string | number | boolean | ... | (string | number | boolean | ... | (string | number | boolean | ... | (string | number | boolean | ... | (string | ... 4 more ... | null)[] | null)[] | null)[] | null)[] | null; } | (string | ... 4 more ... | null)[] | null
                        )[]
                        | null;
                    };
                    url?: {
                        [key: string]: | string
                        | number
                        | boolean
                        | (
                            { [x: string]: string | number | boolean | ... | (string | number | boolean | ... | (string | number | boolean | ... | (string | number | boolean | ... | (string | number | boolean | ... | (string | ... 4 more ... | null)[] | null)[] | null)[] | null)[] | null)[] | null; }
                        )
                        | (
                            string | number | boolean | { [x: string]: string | number | boolean | ... | (string | number | boolean | ... | (string | number | boolean | ... | (string | number | boolean | ... | (string | ... 4 more ... | null)[] | null)[] | null)[] | null)[] | null; } | (string | ... 4 more ... | null)[] | null
                        )[]
                        | null;
                    };
                    [key: string]: | string
                    | number
                    | boolean
                    | {
                        [key: string]: string | number | boolean | { [x: string]: string | number | boolean | ... | (string | number | boolean | ... | (string | number | boolean | ... | (string | number | boolean | ... | (string | ... 4 more ... | null)[] | null)[] | null)[] | null)[] | null; } | (string | ... 4 more ... | null)[] | null;
                    }
                    | (
                        string | number | boolean | { [x: string]: string | number | boolean | ... | (string | number | boolean | ... | (string | number | boolean | ... | (string | number | boolean | ... | (string | ... 4 more ... | null)[] | null)[] | null)[] | null)[] | null; } | (string | ... 4 more ... | null)[] | null
                    )[]
                    | null;
                };
                experimental?: {
                    [key: string]: {
                        [key: string]: | string
                        | number
                        | boolean
                        | (
                            { [x: string]: string | number | boolean | ... | (string | number | boolean | ... | (string | number | boolean | ... | (string | number | boolean | ... | (string | number | boolean | ... | (string | ... 4 more ... | null)[] | null)[] | null)[] | null)[] | null)[] | null; }
                        )
                        | (
                            string | number | boolean | { [x: string]: string | number | boolean | ... | (string | number | boolean | ... | (string | number | boolean | ... | (string | number | boolean | ... | (string | ... 4 more ... | null)[] | null)[] | null)[] | null)[] | null; } | (string | ... 4 more ... | null)[] | null
                        )[]
                        | null;
                    };
                };
                extensions?: {
                    [key: string]: {
                        [key: string]: | string
                        | number
                        | boolean
                        | (
                            { [x: string]: string | number | boolean | ... | (string | number | boolean | ... | (string | number | boolean | ... | (string | number | boolean | ... | (string | number | boolean | ... | (string | ... 4 more ... | null)[] | null)[] | null)[] | null)[] | null)[] | null; }
                        )
                        | (
                            string | number | boolean | { [x: string]: string | number | boolean | ... | (string | number | boolean | ... | (string | number | boolean | ... | (string | number | boolean | ... | (string | ... 4 more ... | null)[] | null)[] | null)[] | null)[] | null; } | (string | ... 4 more ... | null)[] | null
                        )[]
                        | null;
                    };
                };
                roots?: { listChanged?: boolean };
                sampling?: {
                    context?: {
                        [key: string]:
                            | string
                            | number
                            | boolean
                            | (
                                { [x: string]: string | number | boolean | ... | (string | number | boolean | ... | (string | number | boolean | ... | (string | number | boolean | ... | (string | number | boolean | ... | (string | ... 4 more ... | null)[] | null)[] | null)[] | null)[] | null)[] | null; }
                            )
                            | (
                                string | number | boolean | { [x: string]: string | number | boolean | ... | (string | number | boolean | ... | (string | number | boolean | ... | (string | number | boolean | ... | (string | ... 4 more ... | null)[] | null)[] | null)[] | null)[] | null; } | (string | ... 4 more ... | null)[] | null
                            )[]
                            | null;
                    };
                    tools?: {
                        [key: string]: | string
                        | number
                        | boolean
                        | (
                            { [x: string]: string | number | boolean | ... | (string | number | boolean | ... | (string | number | boolean | ... | (string | number | boolean | ... | (string | number | boolean | ... | (string | ... 4 more ... | null)[] | null)[] | null)[] | null)[] | null)[] | null; }
                        )
                        | (
                            string | number | boolean | { [x: string]: string | number | boolean | ... | (string | number | boolean | ... | (string | number | boolean | ... | (string | number | boolean | ... | (string | ... 4 more ... | null)[] | null)[] | null)[] | null)[] | null; } | (string | ... 4 more ... | null)[] | null
                        )[]
                        | null;
                    };
                };
                tasks?: {
                    cancel?: {
                        [key: string]: | string
                        | number
                        | boolean
                        | (
                            { [x: string]: string | number | boolean | ... | (string | number | boolean | ... | (string | number | boolean | ... | (string | number | boolean | ... | (string | number | boolean | ... | (string | ... 4 more ... | null)[] | null)[] | null)[] | null)[] | null)[] | null; }
                        )
                        | (
                            string | number | boolean | { [x: string]: string | number | boolean | ... | (string | number | boolean | ... | (string | number | boolean | ... | (string | number | boolean | ... | (string | ... 4 more ... | null)[] | null)[] | null)[] | null)[] | null; } | (string | ... 4 more ... | null)[] | null
                        )[]
                        | null;
                    };
                    list?: {
                        [key: string]: | string
                        | number
                        | boolean
                        | (
                            { [x: string]: string | number | boolean | ... | (string | number | boolean | ... | (string | number | boolean | ... | (string | number | boolean | ... | (string | number | boolean | ... | (string | ... 4 more ... | null)[] | null)[] | null)[] | null)[] | null)[] | null; }
                        )
                        | (
                            string | number | boolean | { [x: string]: string | number | boolean | ... | (string | number | boolean | ... | (string | number | boolean | ... | (string | number | boolean | ... | (string | ... 4 more ... | null)[] | null)[] | null)[] | null)[] | null; } | (string | ... 4 more ... | null)[] | null
                        )[]
                        | null;
                    };
                    requests?: {
                        elicitation?: {
                            create?: {
                                [key: string]: | (...)
                                | (...)
                                | (...)
                                | (...)
                                | (...)
                                | (...)
                                | (...);
                            };
                            [key: string]: unknown;
                        };
                        sampling?: {
                            createMessage?: {
                                [key: string]: | (...)
                                | (...)
                                | (...)
                                | (...)
                                | (...)
                                | (...)
                                | (...);
                            };
                            [key: string]: unknown;
                        };
                        [key: string]: unknown;
                    };
                    [key: string]: unknown;
                };
            }
            | null
            | undefined

        The client capabilities from the initialize response

      Returns McpUiClientCapabilities | undefined

      The MCP Apps capability settings, or undefined if not supported

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

        if (uiCap?.mimeTypes?.includes(RESOURCE_MIME_TYPE)) {
          // App-enhanced tool
          registerAppTool(
            server,
            "weather",
            {
              description: "Get weather information with interactive dashboard",
              _meta: { ui: { resourceUri: "ui://weather/dashboard" } },
            },
            weatherHandler,
          );
        } else {
          // Text-only fallback
          server.registerTool(
            "weather",
            {
              description: "Get weather information",
            },
            textWeatherHandler,
          );
        }
      };

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