Looks like it's just a GET based API. You don't need a custom plugin for such usage. I recommend using CBSubs URL to send a GET request to their API endpoint formatted as needed. Can also use CB Auto Actions and its Request action to do this.

We're trying to avoid having to make custom solutions for every need, but instead generalized ones that let you use the API of whatever you're wanting to integrate. This significantly makes it easier to maintain on our end and reduces risk of us deprecating a plugin.