Hi @Leonardo A. Barbastefano , yes this is possible! Create a technical profile in your custom policy that specifies the REST API endpoint and the method to call it (GET or POST). You will also need to define the input and output claims for this technical profile.
You'd then configure the technical profile to call the REST API endpoint and retrieve the URIs.
Once the URIs are retrieved from the REST API, you can use them in your policy by referencing the output claims of the technical profile.
This document does a good job detailing this.
I hope that helps! Please let me know if you have any questions and I can help you further.
If this answer helps you please mark "Accept Answer" so other users can reference it.
Thank you,
James