4. Add what it does
The thing you actually wanted to build — as long as it takes.
Two ways to add things.
Ready-made features
Some capabilities ship as installable recipes — payments, file uploads, email, roles and permissions, translations, AI chat, a small game. Ask what is there:
List the recipes available in this project and explain in plain language what each one adds.
Then: Add the <name> recipe and tell me what I need to do to finish setting it up.
Anything else
Describe it the way you would to a new colleague — what the user sees and what should happen, not how to build it:
I want the people who use this to be able to do this thing. They should see what it looks like. When they do something, this should happen. Build the whole thing end to end — database, screens, and tests — and show me the working page in the browser when it is done.
Say "end to end" and "show me the working page"
Every time. Without those words an assistant will often build the invisible half, report success, and leave you with nothing to click. The project's own rules say a feature is not done until you can use it in a browser — these phrases hold your assistant to that.
Done when
You can click through the new feature yourself in the browser.