Added clarification - no bot support

msteams-platform/concepts/authentication/auth-silent-AAD.md

@@ -6,12 +6,15 @@ ms.date: 02/28/2018
 ---
 # Silent authentication
 
-Silent authentication in Azure Active Directory (AAD) is a simplified form of single sign-on (SSO). It's purpose it to minimize the number of times a user needs to enter login credentials while using your app.
+Silent authentication in Azure Active Directory (AAD) is a simplified form of single sign-on (SSO). Its purpose it to minimize the number of times a user needs to enter login credentials while using your app.
 
-If you want to keep your code completely client-side, you can use the [Azure Active Directory Authentication Library](https://docs.microsoft.com/en-us/azure/active-directory/develop/active-directory-authentication-libraries) for JavaScript to attempt to acquire an Azure AD access token silently. This means that the user may never see a popup dialog.
+If you want to keep your code completely client-side, you can use the [Azure Active Directory Authentication Library](https://docs.microsoft.com/en-us/azure/active-directory/develop/active-directory-authentication-libraries) for JavaScript to attempt to acquire an Azure AD access token silently. This means that the user may never see a popup dialog if they have signed in recently.
 
 Even though the ADAL.js library is optimized for AngularJS applications, it also works with pure JavaScript single-page applications.
 
+> [!NOTE]
+> Currently, silent authentication only works for tabs. It does not yet work when signing in from a bot.
+
 ## How silent authentication works
 
 The ADAL.js library creates a hidden iframe for OAuth implicit grant flow, but it specifies `prompt=none` so that AAD never shows the login page. If user interaction is required because the user needs to log in or grant access to the application, Azure AD will immediately return an error that ADAL.js then reports to your app. At this point your app can show a login button if needed.