The latest update for LoLTool is now live and if you run the launcher it should download and install it automatically. Some details follow below.
So Riot ships a SQLite database with the League client that used to contain all the item data (names, descriptions, cost, etc…) needed to make the whole recommended item editor work. Then, for some reason, they removed all of that data. Presumably they updated how the client gets the data internally and didn’t want to maintain a duplicate copy of the data. Fair enough, but a giant pain for me. It’s probably all in the game client data somewhere, but I never managed to decode those files. So I’ve switched to using the Riot API instead. All the item data can be retrieved from the Riot servers and supposedly this does not count against the rate limit for Riot API requests with a developer key. Hopefully this works for everyone; as per usual my testing is limited to my personal dev machine. If things are broken for you make sure you email me and let me know so that I can investigate. Thank you all, and good luck out on the Rift!