No, It is not necessary to create an API integration with your own external system.
One of the benefits using the Shortcut app is that you can access information in your external systems by being logged in your browser in both Zendesk and your own external system.
This means no data is sent through any server and therefore prevents a security risk.
Articles in this section
What are the benefits of using Shortcuts for Zendesk?
Do you need an API integration with an external system?
What's the difference between a bookmark and Shortcuts?
How is the data of the external system secured?
Which data does Sparkly store?
How do you activate Zendesk Sunshine and why do you need it?
My backoffice doesn't have an orderID in the URL, how do you link to it?
I can't seem to create the correct Shortcut, can you help me?