I have written a script that interpolates the beginning and end keyframes of an animation intended to be cyclic in response to my own question here.

The addon executes just fine, but only after clicking in the Fcurve window. I mean, I select, in the fcurve window, some keyframe or keyframe range or keyframe set (the script will look for the underlying channel or curve selected), then I click in my addon within its menu and finally left-click on an empty space in the window for the script to render on.

So, how could I set or fix the script so that it executes when I click on it in the menu?

The code is in Github.

PS: I don't know if the preferred behavior is posting the whole code here or referring it by a link, sorry.