Google Assistant can read the notification from 3rd-party apps like WhatsApp
Google Assistant can read SMS messages from native Messages applications or Hangouts, but it’s reading range is very limited, such as WhatsApp, Telegram, Slack, Discord, GroupMe and other applications. However, it has been learned that this situation has changed in the past few days, and Google Assistant can not only read the text from these applications but also reply. If you want to implement this action, you first need to issue the “read my messages” command to the Assistant.
To do this in this way, you need to enable Google Assistant access your notification by authorizing Google app notifications.
The interface then jumps out of the last incoming message and reads it out aloud, including its source of application and the sender’s name. After that, the user can choose to type or dictate the reply. When this is all done, this message will be marked as read.
In addition, the user can also perform this operation on the most recent messages, and the Assistant will display a series of chat records that have been received and view them one by one.
The last thing to note is that the images, videos, and audio contained in the message are not accessible. For example, Assistant only says that “the message just contains an audio attachment,”, but it will not play it.
Source: androidpolice