As I understand it, XML-RPC is a kludge to get from MarsEdit to MB, because Daniel has not got anything like micropub in any of the other platforms he is supporting. I know people are developing micropub to XML-RPC bridges, but far better in my view is to wait until MarsEdit supports micro pub -- or use another client that does.

// You might be able to use Quill. https://quill.p3k.io/ Depends if you can be authenticated or not.