Test one: ask it something your material doesn't cover
Upload a single lecture — one deck, one chapter, so you know exactly what's in it. Ask a question it definitely answers. Fine, everyone passes that.
Now ask about a topic from a completely different week. Read the answer very carefully. Did it tell you the material doesn't cover this? Or did it produce a fluent, plausible, sourceless answer?
If it did the second thing, you have learned something decisive: for every future answer, you have no way to tell which mode it was in. That's not a small flaw — it makes every answer unverifiable. The full argument.
Test two: ask what its spaced repetition algorithm is
"Spaced repetition" is claimed by nearly every product in this category and implemented properly by very few. Most of it is a fixed ladder — one day, three days, a week — which is a reminder schedule, not a memory model, and it wastes most of the review time it takes from you.
A real answer names an algorithm: FSRS, SM-2. If the vendor cannot name one, they do not have one. Why this matters.
Three more that take thirty seconds
- Does every answer cite a page? Not "sources" — a page, clickable, in *your* document.
- What happens to your uploads? Used for training? Shared? Deleted with your account?
- Can you leave? Export your data, cancel in two clicks, keep access to the period you paid for.