Massive and frequently goods update

Hi!

I`m representing quite a big online shop, we have lots of categories and a huge amount of goods. Each day our partners provide us with new information about their goods. It can be price change, adding a new good item, item removal, etc. Also they provide us with extremely detailed goods descriptions through their partner API. I need to update goods prices and descriptions almost each day and it will be real royal pain to do this manually. So I want to write some util which will obtain prices (mostly in csv or xls format), descriptions (through rest api) and will put it in our shop. The problem is - I was unable to find any documentation neither about opencart partner API nor about opencard db structure. I even don't need to host this util as a opencart module, I can run it locally.

I will appreciate any help.