This is the third and final part of a little series. In part 1 I worked out the workflow: let the AI build the plan with you instead of writing it alone. In part 2 I shared the actual prompts that make an agent plan with you. This one is about the single habit that made the biggest difference of all — and the one I resisted the longest.
It's writing down what the app should not do.
Why I ignored this for so long
For a long time my instinct was simple: tell the AI what to build and how to work, and that's it. Describing what not to build felt pointless. Why spend words on features I'm not even making?
Then I noticed a pattern. I'd agree on a clean, small plan with the agent. Then a few prompts later, while building something unrelated, it would casually add an admin panel I never asked for. Or wire up a payment flow "to be helpful." Or refactor a simple feature into a multi-tenant architecture. Every time, I'd lose an afternoon pulling out work I never wanted.
