Customize the Response - HTML

We have a task url that is triggered from an application we use. The application has an embedded web browser which also shows the response back from our pipeline. This is how the user knows if the task was successfully run or not (I’ve uploaded an image of the browser after the task is completed).

I would like to customize/configure this resulting response back to the user so that it looks nicer. Does anyone know where/how to have it return something nicer looking (without having to point to a separate web server URL)?