I Took the Pick Away From the Engine

For a while my underwriting engine had a habit I didn't like. It would run a house through every exit, pick the winner, and tell me to buy.

Most days that was fine. Then on one deal it said buy, picked wholetail, and saved that choice to the property. The comps behind it had failed their own check. Nobody chose wholetail. The engine did, and the record made it look like me.

That kind of mistake doesn't show up right away. A month later I'm looking at that deal and the file says I picked the exit. I didn't. Now I'm making decisions on top of a choice nobody made.

What I changed

The engine still does the math. Every exit gets measured against my buy box: what it nets, whether it hits my target, how far off it is, and the most I can pay. It's good at that and I'm keeping it.

What it lost is the pick. There's no verdict, best strategy or score telling me to buy. If the comps are weak, the deal gets one status, check the ARV, and waits on that. Then I choose the exit, and the record says who chose it and when. My own pick, a default from my buy box, or one I confirmed in chat each get their own label.

Why it matters past my desk

I've been writing about this in the newsletter. Numbers come from my database and my engines, never from a model's memory. Paper beats records, and records beat somebody said.

This is the same rule pointed at my own software. An engine's pick is a kind of somebody said. It sounds sure. It's still a guess about what I'd want, and it never saw the house on the walkthrough.

Measuring is a job for the machine. Choosing is a job for the person who signs. Mix the two up and later you can't tell which one made the call.

What it cost

The change touched the shared database, the tool server, the web app and both phone apps. Old fields had to come out in order so nothing broke in the middle, and some of that cleanup is still finishing.

I also gave up a little convenience. I used to glance at a verdict. Now I look at every exit and decide, which takes a minute longer. I'll take that trade.

If your tools pick for you, how would you know later who made the call?