In my research to add this feature to OSx finder I also found it is a lot easier to do the same in Windows or Linux OS. But here it is for OSX
From the left most pane select Utilities then in the middle pane select Run Shell Script and drag and drop it to the right pane.
You can do the same process for Application too, i.e. like those in /Applications folder. once you save it as yourPythonTool.app drag and drop to finder toolbar. and run from there. Here is how I have for application I saved.