"Set an alarm for 4:15" would work. Or "remind me to pick up a newspaper at 9:15". You can add and delete things from a shopping list - just "add bread to the shopping list" or "remove bread from the shopping list", then when you need it, "show me the shopping list". I use mine for some pretty mundane things too, like "set the screen brightness to 20%". It's all I need at home. (15% is just a touch too dark.)
It's about as much AI as cars were cars in 1875 - just before the beginning. (Your car was painted, in the factory, by an AI device. Just the metal, not much, if any, overspray. Still primitive.) But it can be handy for a few things, depending on what you need. So lists, alarms and reminders would probably be all you'd want to use it for. (If your phone is online, you can ask it anything, and it will use the default search engine [Google] to search for what you ask it. If you ask if it's going to rain today, you'll get the whole weather thing - the range of temperatures today, the current conditions, and what you'd get if you typed the question into Google. Still pretty primitive.)
(I maintain my own shopping list text file, so a couple of taps and I can add a number to an item - no number means "I don't need any this time". But Google Assistant would do about the same thing - I'm just used to my text file.)
One day, we'll consider today's supercomputers primitive first attempts (the original "supercomputer", the CDC 6600, could do an "amazing" 500kflops - something your phone can in addition to playing an intense game on it), and AI will be able to actually figure out more than just what you meant by what you said.