Update README.md

README.md

@@ -134,12 +134,13 @@ Opening EcoAssist for the first time will take a bit longer than usual due to sc
 <summary><b>macOS</b></summary>
 <br>
 
-1. Download and open [this file](https://PetervanLunteren.github.io/EcoAssist/install.command). Some computers can be quite reluctant when having to open command files downloaded from the internet. You can circumvent trust issues by opening it with right-click > open > open. If that still doesn't work, you can change the file permissions by opening a new terminal window and copy-pasting the following commands.
+1. EcoAssist requires you to have a recent version of Xcode Developer Tools. You can donwload and install it from the [Mac App Store](https://apps.apple.com/us/app/xcode/id497799835?mt=12). 
+2. Download and open [this file](https://PetervanLunteren.github.io/EcoAssist/install.command). Some computers can be quite reluctant when having to open command files downloaded from the internet. You can circumvent trust issues by opening it with right-click > open > open. If that still doesn't work, you can change the file permissions by opening a new terminal window and copy-pasting the following commands.
 ```bash
 chmod 755 $HOME/Downloads/install.command
 bash $HOME/Downloads/install.command
 ```
-2. If you're an Apple Silicon user (M1/M2), go for a nice walk because this may take about 30 minutes to complete. Some of the software packages are not yet adopted to the Apple Silicon processor. There is a workaround, but it takes some time. In order to make MegaDetector work on Apple Silicon computers, the guys at [Ecologize](http://ecologize.org/) had to re-build the model with *slightly* different results. The bounding boxes appear to be the same to around two decimal places in both location and confidence, which is good, but not *exactly* the same. Please keep in mind that this is an unvalidated version of MegaDetector, and they don't exactly know how it compares to the validated version since it is much less tested.
+3. If you're an Apple Silicon user (M1/M2), go for a nice walk because this may take about 30 minutes to complete. Some of the software packages are not yet adopted to the Apple Silicon processor. There is a workaround, but it takes some time. In order to make MegaDetector work on Apple Silicon computers, the guys at [Ecologize](http://ecologize.org/) had to re-build the model with *slightly* different results. The bounding boxes appear to be the same to around two decimal places in both location and confidence, which is good, but not *exactly* the same. Please keep in mind that this is an unvalidated version of MegaDetector, and they don't exactly know how it compares to the validated version since it is much less tested.
 4. When the installation is done, you'll find a `EcoAssist.command` file in your `Applications` folder. The app will open when double-clicked. You are free to move this file to a more convenient location. If you want EcoAssist in your dock, manually change `EcoAssist.command` to `EcoAssist.app`, then drag and drop it in your dock and change it back to `EcoAssist.command`. Not the prettiest solution, but it works...
 </details>