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Creating a Mini App

"Even if all you have is the idea, 'I wish there were an app like this,' that's enough. Even if you don't know code, just tell AI what you want in words, and AI will write the code for you."

This document walks you through the entire process, from start to finish, of talking with AI tools like Claude Code and Codex to turn your idea into a working Apps in Toss mini app.

Helpful for people like these

  • People who have never coded at all

  • People who have app ideas but don't know how to get started

  • People who want to quickly build a mini app with help from AI

If you already have a web project, then the existing Web Project Development GuideIf you want to develop with React Native, then React Native Development Guideplease refer to it.

1. Install an AI tool

First, install an AI tool that will build the app for you, and prepare the basic environment needed for development.

Please follow the steps that match the MCP client you're using.

If you already use an AI tool, you can skip this step.

Claude Code is an AI development tool used in the terminal. First, on my computer, claude please check whether you can use the command.

macOS

  1. On the keyboard, Command(⌘) + Spacepress to open Spotlight Search.

  2. Terminaltype it in and press Enter.

  3. When the Terminal window opens, type the command below and press Enter.

claude

Windows

  1. From the Start menu, PowerShellsearch for it and open it.

  2. When the PowerShell window opens, type the command below and press Enter.

claude

When Claude Code runs, please complete the login as well.

claudeIf you see a message saying it can't be found, Claude Code Installation Guideopen it and install the Claude Code CLI according to the operating system you're using. After installation, reopen Terminal or PowerShell and run claudeagain.

Codex can be used in the ChatGPT desktop app.

ChatGPT app download pagedownload and install the installer that matches your operating system (macOS·Windows).

After installation, run the ChatGPT app and log in. In the upper-left, ChatGPT button to Codexselect it.

LogoDownload ChatGPTChatGPTapp

2. Connect the plugin for Apps in Toss development

So that AI can look up the Apps in Toss docs, create the mini app, and register it in the console, apps-in-toss install the plugin.

2-1. Install Git

Git is required before installing the plugin. First, install Git according to the operating system you're using.

Git macOS download pageopen it and install it following the instructions.

On macOS, you only need to install Xcode Command Line Tools, which include Git.

  1. On the keyboard, Command(⌘) + Spacepress to open Spotlight Search.

  2. Terminaltype it in and press Enter.

  3. When the Terminal window opens, paste the command below and press Enter.

  1. When the installation window appears, complete the installation following the instructions.

  2. After installation, turn your AI tool off and on again.

Git for Windows download pageopen it, download the installer, and run it.

On most Windows PCs, choose the item below.

Git for Windows/x64 Setup

Only if you're using an ARM-based Windows device, choose the item below.

Git for Windows/ARM64 Setup

After installation, turn your AI tool off and on again.

If you want to check whether it installed correctly or get stuck midway, try asking Claude Code or Codex like this:

2-2. Install the apps-in-toss plugin

Follow the steps that match the MCP client you're using apps-in-toss and install the plugin.

In Codex, from the Plugins screen in the ChatGPT desktop app, apps-in-toss install the plugin.

  1. Open the ChatGPT desktop app.

  2. In the upper-left, ChatGPT button to Codexswitch to

  3. Open the Plugins settings on the Codex screen.

  4. Click the Add Marketplace button.

  5. On the screen, Sourceto toss/apps-in-toss-harness and add it.

  6. The newly added apps-in-toss install the plugin.

  7. apps-in-toss-console complete the login.

  8. /ait:welcome type it in.

In Claude Code, install the plugin with Claude CLI.

First, open Terminal on macOS or PowerShell on Windows claudeand type it to check whether Claude Code runs.

claude If the command isn't recognized, Claude Code Installation Guideinstall the Claude Code CLI in

If Claude Code is ready, run the commands below in order.

In the Claude conversation, /mcptype it in and apps-in-toss-console log in to

/ait:welcome type it in to check whether the plugin was installed correctly.

3. Develop

From now on, you don't need to memorize complicated commands. Just tell AI in words about the app you want to make, the features you want to add, and the situations you want to test.

Proceed in this order

  1. Describe the app you want to make.

  2. AI organizes the app structure and the needed features.

  3. Build the mini app and prepare the code.

  4. Add the required features one by one.

  5. Test it in the Toss app on my phone.

  6. If there's a problem, ask to have it fixed again with a screenshot.

  7. When you're ready, request a review.

3-1. Planning

Explain your mini app idea to AI. If you make a request like below, AI will check whether it matches Apps in Toss policy and organize and suggest the screens and features you need. If you like the suggestion, proceed as is; if it's different from the direction you want, you can ask again and refine it.

3-2. Build the mini app

A mini app will be registered in Apps in Toss, and a space to hold the code will be created along with it. Try asking like below. {mini app name} Feel free to choose any name you want and put it in that spot.

3-3. Request the features you want

Now it's time to ask AI for the features you want one by one. Just tell it what features you need, and AI will build them while checking the Apps in Toss docs. You can also refer to the feature documentationprovided by Apps in Toss.

How to ask AI well

  • Be as specific as possible

    • Instead of saying 'make a button,' it's more accurate to say something like 'make a Start button in the center of the screen, and have it show a reward ad when tapped.'

  • It's okay if it's not perfect the first time

    • If there's something you don't like, you can casually ask again, like 'Please change this part like this.'

Watch a video of the mini app being built

3-4. Connect an external storage service

In the mini app, Storage APIcan be used to store data. However, because this data is stored in the user's device environment, it may disappear if the device is changed or the app data is reset.

If you have data that needs to be checked again on other devices or kept for a long time, such as posts left by users, lists of favorited items, or saved nicknames, connect an external storage service. If there is no data that must be kept after a device change, you can skip this step.

For external storage, you can use services such as Supabase, Firebase, or Cloudflare. There is a free tier to get started, but costs may arise as usage increases or if you use paid features. Before applying it for real, check each service's latest pricing plan, limitations, and whether it can be integrated with the mini app.

  • Supabase: A backend service that provides a PostgreSQL-based database. It can be used to store structured data such as posts, user settings, and favorite lists.

  • Firebase: A backend service provided by Google. You can use Firestore or Realtime Database to store the data needed by the app externally.

  • Cloudflare: Provides infrastructure services with fast response times. It can be used with Workers KV, D1, R2, and so on to store relatively light data or files.

Please check the security settings

By default, external storage is often in a state where anyone can access the data.

If you ask AI, 'Please check the security settings too,' it will guide you on how to set it up safely.

Some parts need to be run directly in the service dashboard, so please follow along as AI guides you.

4. Test and release

A mini app isn't only testable after it's completely built. It's okay to test it little by little whenever you're curious about a screen during development.

4-1. Test with the Toss app

You can test the mini app in the Toss app on your phone. Try asking like below. AI will prepare it so it can be tested and guide you on how to open it on your phone.

Conditions needed for testing

  • You must be logged in to the Toss app.

  • You must be a workspace member.

  • You must be at least 19 years old.

If you see an error or a strange screen, take a screenshot and show it to AI. AI can't see the actual device screen, so if you explain it along with a screenshot, it will fix it more accurately.

If it's not working the way you want, feel free to ask again like 'Please change this part like this.' You can test again after making the changes. (e.g., 'Move the banner ad on the main screen a little lower')

If you want to prevent errors in advance, try asking to integrate Sentry. Because AI can check the logs directly when an error occurs, it can find the cause faster and more accurately.

Watch a video of testing in the Toss app

4-2. Release

To release a mini app, it first has to pass Apps in Toss team review. Review is the process of checking whether the mini app follows the policy and guidelines well. Once testing is done, request a review.

The review results will be sent through the console and by email. If the review is approved, you must press the 'Release' button in the console to make the mini app available to users. Once released, it will be reflected in the Toss mini app list after 1 hour.

After making the app, to reach users, marketing guideplease also refer to it.