You created a group DM

Facts

Required scopes

Works with

RTMEvents API
{
    "type": "group_open",
    "user": "U024BE7LH",
    "channel": "G024BE91L"
}

The group_open event is sent to all connections for a user when a group Direct Message (or mpim) is opened by that user.

This event is not available to bot user subscriptions in the Events API.