Out of my curiosity, where did you get that event filter from? I don't see it in the list of event filters in the API reference.

So instead of asking such a question, ask how to get Team Messaging Task notification events.

In fact, you just need to subscribe for the ''/restapi/v1.0/glip/posts' event and detect the type in the event payload. E.g.

{

  "id": "37742841397252",

  "groupId": "1152743292930",

  "type": "TextMessage",

  ...

  "attachments": [

    {

      ...

      "section": "Delete",

      "status": "Pending",

      "subject": "Check and clean up",

      "type": "Task"

    }

  ],

  ...

  "eventType": "PostAdded"

}

Yeah, great, but how it will help me to catch an event on update (title, assignees, due datetime, e.t.c.) a task?