Look inside your own app with Claude: the REA setup steps and the first 3 questions

REA is a free, open-source add-on (MIT license) that lets Claude look inside an app and explain how it works, with the evidence. Here are the setup steps for Claude Code or the Claude desktop app, and the first 3 questions to ask Claude about an app you built or are allowed to examine.

The one rule first

Use REA only on software you own or are authorized to examine. That's the project's own rule (README and DISCLAIMER.md on github.com/morluto/rea). An app you built, an app Claude built for you, or an open-source app whose license allows it are good first targets.

The makers also say what REA will not help with: cracking license checks or copy protection, game cheats, getting into systems you're not allowed to test, and copying someone else's paid software or its code. Owning a copy of an app doesn't automatically give you permission for everything. When in doubt, don't.

What you need first

Claude Code or the Claude desktop app. Claude Code needs a paid Claude plan (Pro, Max, Team or Enterprise). I haven't confirmed whether the desktop route works on the free plan, so check your plan first.
Node.js 22.19 or newer (24.11+ and 26+ also work). Open your terminal and type node -v to see your version. If it's older or missing, install the LTS version from nodejs.org.
About 10 minutes. Native apps (not JavaScript) need an extra engine like Ghidra or Hopper. Skip that for your first try.

The setup steps

If you use the Claude desktop app, quit it fully first (a running app can overwrite the new setting).
In your terminal, run: npx rea-agents setup
npm asks to download the package. That's a separate yes from REA's own question.
Pick your agent: Claude Code or Claude Desktop. Leave the others unticked.
Read the plan before you say yes. It lists every file it will change. For Claude Code that's ~/.claude.json (it adds REA as a tool) and one skill in ~/.claude/skills. It makes a backup of your settings first.
It may offer to install Hopper. Say no for now. You don't need it for JavaScript or Electron apps.
Approve, then restart Claude.
Check it worked: npx rea-agents doctor --client claude_code --skill --json (for Claude Code). In Claude Code you can also type claude mcp list and look for rea.
Want it gone later? npx rea-agents@latest uninstall removes only what REA added.

Heads-up: in Claude Code, setup adds REA for every project you open, not just one. The REA installation guide shows how to limit it to one project if you prefer.

The first 3 questions to ask Claude

Replace the parts in brackets with your own app. Start each one in a new chat.

1. What is this app made of?

Paste this

Use REA to look at [the folder or file of my app]. In plain English, tell me what this app is made of: the main parts and what each one does. Show the evidence for each part. Tell me what you couldn't find or aren't sure about.

2. How does one feature work?

Paste this

How does [the feature, for example search or export] work in this app? Walk me through it step by step, in plain English. Show me the files or functions you found, and mark anything you're guessing.

3. What does it talk to?

Paste this

Does this app talk to the internet? List the web addresses you can find in its code and what each one seems to be for. Show the evidence, and tell me what you can't confirm without running the app. Don't open, copy or send any personal data.

The honest part

Check the proof. REA's own disclaimer says results can be incomplete or wrong. Claude shows you where it looked, so open that file and read it before you trust the answer.
REA runs the analysis on your computer, but Claude still reads the results. Your Claude plan's data rules apply to what it sees. Don't point it at apps full of customer data.
An explanation of how an app works doesn't give you the right to copy it. Use what you learn on your own work.
REA changes fast. If something fails, run npx rea-agents@latest setup again to get the newest version.

As of October 21, 2026, REA has over 350,000 stars on GitHub and was the number one repo on GitHub Trending that week. Menus, versions and plans change.

Sources: github.com/morluto/rea (README, DISCLAIMER.md, docs/installation.md), read October 21, 2026; support.claude.com (Use Claude Code with your Pro or Max plan).