With VMC on AWS, one can utilise the REST API which comes with NSX-T.
You can find an excellent Video about the same on the below link, which demoes the use of the NSX REST API in conjunction with VMware Cloud on AWS.
Direct link to the Video by Humair Ahmed:
VMware Cloud on AWS: Automation with NSX REST APIs - YouTube
In addition to the above Video, you can also find more Information on automating your VMware Cloud on AWS SDDC in this free ebook:
VMware_Cloud_on_AWS_NSX_Networking_and_Security_eBook (Chapter 8).
I hope this is informative for you and please feel free to ask any questions you may have.
/Rick