# Build an Atrium app with AI

Build a COHO Atrium app by describing it to an AI coding tool. COHO hosts it for you.

You don't need to write code to build an Atrium app. You describe what you want to an AI coding tool, it writes the app, and **COHO hosts it for you**, so there's no server to run.

<AdkQuickStart />

## What an Atrium app is

An Atrium app is a small web service that plugs into COHO. Once a manager connects it in the COHO Store, COHO can:

- tell your app when something happens, for example when a tenancy starts or ends
- give your app a key so it can read and update data in COHO through the COHO API
- show your app's own screen inside COHO, if it has one

Your app lives outside COHO. COHO never runs your logic itself; it calls your app and your app calls COHO back.

## What you can build

<CardGrid>
	<Card title="A helper that runs in the background" icon="rocket">
		No screen at all. It reacts to events or runs on a timetable, for example sending a welcome message when a tenancy starts.
	</Card>
	<Card title="A panel inside COHO" icon="document">
		Your own page, shown inside COHO when a manager opens your app from the Store.
	</Card>
	<Card title="A settings form" icon="setting">
		A few simple preferences managers fill in from the Store, such as a send time or a subject line.
	</Card>
</CardGrid>

Apps can combine these. Not every app needs a screen.

## How it works

1. **Try it safely on Playground** (recommended): a separate copy of COHO with demo data, so you can see what you're building without touching real customers.
2. **Give your AI the Atrium ADK** (use the box above) and describe what you want.
3. **Your AI builds the app and COHO hosts it.** You approve every step.
4. **Connect the app in the COHO Store** and try it out, first on Playground, then in your real organisation.

<LinkButton href="./what-you-need/" icon="right-arrow">What you need</LinkButton>

:::tip[Every app starts private]
Apps you build this way are private to your organisation. Listing an app publicly in the COHO Store needs a quality check first. See [Get help](./get-help/#when-to-bring-in-a-developer).
:::