The following information is derived from the plugin description.

The External CoWork Message Sending plugin provides a Task Planner action to send messages to a configurable, external CoWork server.

While CoWork itself has the ability to send messages using the Task Planner to itself, this plugin will use the WebAPI of an external CoWork server to deliver messages. It is necessary to configure the external server with WebAPI and enable the token authentication plugin. Additionally, set up a user who has access to CoWork with a Bearer token.

Messages will be sent by the user who has the Bearer token, and can only be sent to channels that the same user is a member of. Therefore, it is advisable to use a restricted user who only has CoWork access to the minimum number of required channels.