Using the store api to pull products from a custom database

I think I’ve read it correctly, but want to make sure I haven’t over looked something.
I want to be able to insert products into the store from a custom database. I’m not trying to have a database that “is” the store; I’m happy to insert and create into the store by pulling data out of my custom database - but - I don’t think the API allows that. Can someone confirm?
Am I correct that this isn’t possible? or is it possible and I’ve overlooked the API to insert, remove, price items in the store?