01What REA Reverse Engineer Anything Is and How It Works
REA Reverse Engineer Anything is a free open-source tool that uses AI agents to take apart apps, websites, and tools so you can understand how they work and build your own version. Think of it like having a smart assistant that looks under the hood of any software and then makes a custom copy for you.
REA stands for Reverse Engineer Anything. It runs as an MCP, which is a standard way for AI agents to connect to external data. You give it a target, like a website or an app, and it inspects the backend code and rules.
Then it returns all the findings to your AI agent. The agent uses that information to create a new app that does the same thing, but with your own customizations.
In this episode, Julian Goldie shows how he used REA to reverse engineer Go High Level's calendar system. The tool found the API, the meeting length, the buffer times, and even the booking window. Then it built a working calendar app that was better than the original—and it took only five minutes.
02Main Features of REA
REA comes with several powerful features that make it easy to tear down and rebuild software. Here are the key ones:
- Free and open source: You don't pay anything, and the code is public on GitHub. The repo has over 192,000 stars and is growing fast.
- Works with any AI agent: You can use REA with Claude, Hermes, Anti-Gravity, or any agent that supports MCP. This gives you flexibility to choose the best AI for your project.
- Extracts APIs and rules: REA doesn't just copy the look of an app. It digs into the backend and finds the actual APIs, scheduling rules, and logic that make the app run.
- Recreates apps with changes: The tool builds a new app that uses the same APIs and rules, but you can customize everything. For example, you can change meeting lengths, add new fields, or embed the app in your own website.
- Works on multiple targets: REA can reverse engineer websites, apps, devices, and even Android APK files. This means you can take apart mobile apps too.
03How to Set Up REA
Setting up REA is straightforward. You do not need to be a developer to get started. Julian showed exactly how he did it inside his agentic operating system.
Follow these steps:
- Get an AI agent: Choose one that supports MCP, like Claude or Hermes. You will need a terminal or an agentic OS to run it.
- Install the MCP: Download the REA MCP from GitHub. It is a free open-source package. The GitHub link is in the description of this episode.
- Connect the MCP to your agent: Follow the standard setup for your AI agent to connect the MCP. This usually takes just a few commands in the terminal.
- Give it a target: Tell REA what you want to reverse engineer. For example, you can say "analyze the calendar system in Go High Level" or "find the search feature in the Notes app."
- Let it run: REA will inspect the target, read the code and rules, and return the evidence to your agent. Julian said this takes about five minutes for a simple app.
- Ask your agent to build: Once the evidence is ready, tell your AI agent to create a new app based on what REA found. You can add custom prompts to make the app unique.
04How to Use REA to Build Your Own App
Julian demonstrated how he used REA to create a custom calendar app for his SEO agency. Here is how you can do the same for any tool you use.
First, you identify a tool you are currently paying for or that has a feature you like. In the episode, Julian chose the Go High Level calendar system, which works just like Calendly. He gave REA the command to reverse engineer the system for calendars inside Go High Level.
Second, REA went to work. It inspected the backend of the calendar, found the scheduling rules, the slot interval, the buffer times, and even the number of seats. It also identified the API that the app uses.
Then it returned all this information to Julian's AI agent.
Third, the AI agent used that data to build a new calendar app. The app kept the same booking window and meeting length, but it was now fully customizable. Julian could change any sentence on the left side of the screen, and the calendar in the middle would update instantly.
He could also embed the calendar into his funnels and compare it with the live Go High Level calendar.
The result was a free app that did everything the paid version did, but with more control and no monthly fee.
05Results and Comparisons from the Episode
Julian tested REA by building a calendar app and comparing it to the original Go High Level system. Here are the results he shared.
The new app was fully functional. It could fetch real time slots and compare them with the live Go High Level calendar. Julian said the app was "better in some ways" because it was more customizable.
He could change the meeting length, the buffer times, and other rules exactly how he wanted.
The original Go High Level calendar costs money each month. The REA-built version was completely free to use. It also did not lock Julian into someone else's pre-made templates.
He owned the new app and could modify it anytime.
Julian noted that the tool is not about copying someone else's app exactly. It is about creating something unique and personalized. The new calendar app kept the same core functionality but added flexibility that the original did not have.
He also mentioned that REA can be used to research competitors. You can ask it to analyze a single feature of an app, then use that evidence to build that feature into your own product.
06Tips, Limits, and Mistakes to Avoid
Using REA is powerful, but there are some things to keep in mind. Julian shared a few tips and warnings.
Always create something new. Do not just copy another app and claim it as your own. REA is designed for research and personalization.
Use it to build a tool that is tailored to you, not a clone. That is how you avoid legal trouble.
You do not need to be technical. The tool returns evidence in plain language. Julian said "you don't need to be technical to understand this." The AI agent handles the coding.
However, some developers may want to use the terminal, but Julian personally avoids it. He recommends using an agentic operating system or a graphical interface instead.
One limitation: the tool works best on relatively simple apps. Julian said think of tools like a to-do list, a calendar, or a notes app. Very complex apps may take longer or be harder to reverse engineer.
Finally, REA is free but it requires an AI agent that supports MCP. If you do not have one, you will need to set that up first.
07Who REA Is For and Why It Matters
REA is for anyone who wants to build their own tools without hiring a developer or paying monthly software fees. Julian believes that mediocre apps will disappear in the next five years because people will just build their own personalized versions.
It is perfect for business owners, freelancers, and creators who rely on simple apps like calendars, schedulers, or CRM systems. You can take the features you like from any app and create a version that fits your exact workflow.
Julian also points out that REA works well for testing competitors. If you are building a product, you can use REA to analyze a specific feature and then add that feature to your own app. This speeds up development and helps you stay ahead.
In the episode, Julian says he thinks the future is about owning your own apps instead of renting them. With REA, you can already do that today. It is a free tool that puts the power of software creation into everyone's hands.
