https://os.mbed.com/docs/mbed-os/v5.12/tools/windows.html Near the bottom, step 4. Set up the environment claims to give an example but the path is given as <path to ARM bin> which is a generality and not a specific example. The latter would have been helpful because I am not sure if the \bin\ part is supposed to be in there, and whether any space characters are allowed in the path. Using the GNU tools installer produces an install tree full of paths containing spaces. The Ac6 tools do not install that way, so I wonder if one of the reasons my mbedcli does not work is because of that. Hmm. Maybe the ARM compiler installs on a windows box in a space-free way. By the way, the name of the mbed cli binary can be changed any time as far as I am concerned. It is ungoogleable. Even mbedcli etc. would have been better.