Adding Dynamic Approvers to Requested item using Api

[abhi182000]

I have a requirement where I have a catalog item. 
When the catalog item is submitted, an RITM(sc_req_item) is created. 

My requirement is as follows : 
1. RITM is created 
2. For the approval stage the list of approvers is not present in SNOW , I need to trigger an api to a 3rd party app and the api will send a response with the list of approvers based on the variables selected in the catalog item

So basically Once the RITM is created I need to trigger this api and get the response and populate the approval list.
How can i achieve this? 

I have a workflow attached to this catalog item 
Can i write a script and call the api in the 'advanced' section of the 'approval activity ' in the workflow? 
OR 
Should i run a buisness rule /script include which will call the api and get the response? 
If so could you please mention the flow of this? 

I have 2 levels of approvals . So can I do it directly in the approval action script? 

I have attached the image of the approval activity. 

I'm just starting out with automations in SNOW. Any help would be appreciated 
Thank you in advance 🙂

[DrewW]

I would use a script activity to trigger the call to the web service and also pass over the requested item with the info.  Then add a "Wait for WF Event" activity to the workflow.  From there you can have the 3rd party service make a call back to a scripted rest service to indicate if the request was approved or not and then all you have to do is record that in a workflow var and trigger the workflow event to get the workflow to move forward.  After that its just a matter of checking the workflow var to see if you need to mark the requested item as approved or rejected.