Ok, the /tools/ folder is the problem, in Android Studio 3.6 the SDK Tools are obsolete and not installed by default. I found the way to manually install here:
Android SDK Tools option is missing from SDK Manager in Android Studio 3.6.1
"Launch Android Studio and go to "SDK Manager" - you can launch it after creating a blank project and going "Tools -> SDK Manager" under the "AVD Manager" option. In the new window open "System Settings -> Android SDK". From there pick "SDK Tools". Now you need to uncheck the "Hide Obsolete Packages" option in the bottom of the window. Now there should appear a new option: "Android SDK Tools (Obsolete)" - check that, hit "Apply" - it will download the files and "Tools" folder will appear in the Android folder."
Ironically, Google's own Flutter development tools also depend on the SDK Tools that they have made obsolete.