Retrieving data from referenced app and adding it on Task's description when Workflow is triggered

Hi there.

Exactly how I've outlined above. I am running a booking app which fetch data from customers app and employer app. I've set up a Workflow action that when a certain category's option is clicked, it will create a delegated Task for a colleague of mine. I want the description field of this new Task to contains Employer's address from a referenced app. I've tried the @all.... option to call out for data from this referenced app but it is not working.

Anyone knows a workaround solution for this?