When you install the reference implementation, it creates a console script pathsjson with the following usage:

optional arguments:
  -h, --help           show this help message and exit
  --init               Create a .paths.json file in the cwd
  --init-globals       Create the global paths.json file
  --make-exports       Print exports for Makefile eval
  --print-global-path  Print global paths.json file path
  --shell-exports      Print exports for shell

You'll notice the reference to a global path.json file. This file lets you define user-level defaults. It's useful when you do contract work or group related projects onto one disk. For example, I may define a CONTRACT-99 directory in the global paths.json file. Then, all my data goes onto a portable harddrive for that contract.

The --shell-exports switch prints the resolved paths to the console with with export and quoting. This lets you use the paths in your shell session, via,

eval $(pathsjson --shell-exports)