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AppServer

AppServer (also known as TpaServer in older versions) is the base class for creating Third Party Application (app) servers that handle webhook requests from MentraOS Cloud to manage app sessions. 
import { AppServer } from '@mentra/sdk';

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Constructor

constructor(config: AppServerConfig)
Parameters:

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Methods

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getExpressApp()

Exposes the internal Express app instance for adding custom routes or middleware. 
getExpressApp(): express.Express
Returns: The Express application instance.

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onSession() [protected]

Override this method to handle the initiation of a new app session when a user starts your app. Implement your app’s core logic here (e.g., setting up event listeners). 
protected onSession(
  session: AppSession,
  sessionId: string,
  userId: string
): Promise<void>
Parameters:
  • session: The AppSession instance for this specific user session
  • sessionId: The unique identifier for this session
  • userId: The unique identifier for the user
Returns: A Promise that resolves when session initialization is complete

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onStop() [protected]

Override this method to handle cleanup when an app session is stopped by the user or system. 
protected onStop(
  sessionId: string,
  userId: string,
  reason: string
): Promise<void>
Parameters:
  • sessionId: The unique identifier for the session being stopped
  • userId: The unique identifier for the user
  • reason: The reason the session was stopped (‘user_disabled’, ‘system_stop’, ‘error’)
Returns: A Promise that resolves when session cleanup is complete

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onToolCall() [protected]

Override this method to handle tool calls from Mira AI. This is where you implement your app’s tool functionality. For a comprehensive guide on implementing AI tools, see AI Tools. 
protected onToolCall(
  toolCall: ToolCall
): Promise<string | undefined>
Parameters:
  • toolCall: A ToolCall object containing the tool ID, parameters, user ID, and timestamp
Returns: A Promise that resolves to an optional string response that will be sent back to Mira Example: 
protected async onToolCall(toolCall: ToolCall): Promise<string | undefined> {
  console.log(`Tool called: ${toolCall.toolId}`);
  console.log(`Tool call timestamp: ${toolCall.timestamp}`);
  console.log(`Tool call userId: ${toolCall.userId}`);

  if (toolCall.toolParameters && Object.keys(toolCall.toolParameters).length > 0) {
    console.log("Tool call parameter values:", toolCall.toolParameters);
  }

  if (toolCall.toolId === "add_todo") {
    const reminder = addReminder(
      toolCall.userId,
      toolCall.toolParameters.todo_item as string,
      toolCall.toolParameters.due_date as string | undefined
    );
    return `Added reminder: ${reminder.text}`;
  }

  return undefined;
}

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start()

Starts the app server, making it listen for incoming webhook requests. 
start(): Promise<void>
Returns: A promise that resolves when the server has successfully started.

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stop()

Gracefully shuts down the app server, cleaning up all active sessions and resources. 
stop(): void

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generateToken() [protected]

Generates a JWT token suitable for app authentication, typically used for webviews. See Token Utilities for more details. 
protected generateToken(
  userId: string,
  sessionId: string,
  secretKey: string
): string
Parameters:
  • userId: The user’s identifier
  • sessionId: The session identifier
  • secretKey: Your app’s secret key (should match the one configured in MentraOS Cloud)
Returns: The generated JWT token string

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addCleanupHandler() [protected]

Registers a function to be executed during the server’s graceful shutdown process. 
protected addCleanupHandler(handler: () => void): void
Parameters:
  • handler: The cleanup function to add

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Configuration

interface AppServerConfig {
  /** Your unique app identifier (e.g., 'org.company.appname'). Must match console.mentra.glass. */
  packageName: string;

  /** Your API key obtained from console.mentra.glass for authentication. */
  apiKey: string;

  /** The port number the app server will listen on. Defaults to 3000. */
  port?: number;

  /** Path to a directory for serving static files (e.g., images, logos). Set to `false` to disable. Defaults to `false`. */
  publicDir?: string | false;

  /** Whether to enable the `/health` endpoint for status checks. Defaults to `true`. */
  healthCheck?: boolean;
}