From what I can see there is no official API (Feature Request here: Official n8n API) but @jan did say in another post (API to make flows in n8n - #3 by jan) that you could work around it by using the same post requests the UI makes to the backend. That could possibly help you out, Maybe you could make a web hook workflow to define a simple API that does what you need and use the HTTP Request node to run it.