I'm really impressed by how unironically good last-place games can be in Adventuron jams, and The Missing Witch is no exception. Perhaps it doesn't soar, but it clearly does more than just make up the numbers, and if you're playing through the whole jam, you won't want to miss it.
You play as a nine-year-old who wants to get into a party and have some adventures. These involve, well, a lost witch. So the beginning is largely reconnaissance. One thing you must find is in your home, and if you dawdle too long, your parents make you stay in. (There's a joke to this. I won't spoil it.) The other things you need are strewn about the scenery, and this might be a pain in Inform with the non-sparse room descriptions, but Adventuron's ability to highlight critical words makes everything easier.
Once you've got a costume for the party, the summoning really starts. I was thrown a bit because I had to remove my costume to reach one semi-hidden room, and I was worried the twins would come after me, but that was relatively trivial. Getting there involves standard item-munging. There's a crypt of sorts to explore at the end, too.
The sorcery involved is decidedly g-rated and, well, it's trivial guess-the-verb. The ending was satisfying. It's a nice balance of kids'-party and minor spoernatural creepiness. So I really recommend playing through. Even if you get stuck, there's only so much to do, and there's one NPC you may forget about that turns out, indeed, to be an obstacle later.
One tip, though: the author added AI art for the 2.0 version now on itch.io, but it's in a 1x1 ratio, meaning you can't see it unless you narrow your browser a good deal. This, however, is worth it, since the graphics do add to the experience.