Hi @j9s3 and @ogibayashi,
Yes, if you are looking to programatically create index patterns, the best approach at the moment is to modify the contents of the .kibana index directly via the Elasticsearch REST API. You can read a bit about the structure of the .kibana index here: https://www.elastic.co/blog/kibana-under-the-hood-object-persistence
Fair Warning: Modifying the .kibana index is, of course, not ideal because the index is meant to be an implementation detail of where Kibana stores its objects (index patterns, visualizations, etc.). It's possible the Kibana developers might change something about the structure/semantics of the documents in this index and that would break your script that's programmatically writing to this index.