A function within my user model validates against the minecraft API.

minecraft_premium.rb

def minecraft_premium
  require 'open-uri'
  url = "https://minecraft.net/haspaid.jsp?user="
  minecraft_validation_url = url + minecraft_username
  is_username_premium = open(minecraft_validation_url).read
  errors.add(:minecraft_username, minecraft_username + " is not a premium minecraft account") unless is_username_premium == "true"
 end