We’re receiving a lot of messages from developers willing to integrate Twitter Cards with prismic.io (an API-based CMS), we’ve set up this guide for them: https://prismic.io/docs/examples/howto-add-twitter-cards
Don’t hesitate to just copy-paste this guide to your CMS Integration Guide here: https://dev.twitter.com/cards/cms-integration
If you’ve got any question, I’m also here to help.
Cheers