Add custom parameter through Core API?

So, I believe I am calling in the Glyphs app core API in my first line,

from Glyphs import *

and based on answers on the forum so far, I don’t think I can directly use the Glyphs Python API in remote scripts. So, there are PyObjC methods to do things, rather than straightforward Python API methods.

Interestingly, I’m realizing that even when I try to set custom parameters through the regular Python API, they only partially set … but don’t actually add new interpolation value fields to the font masters.

font = Glyphs.font

fontAxes = {
	"Weight": "wght",
	"Negative": "NEGA"
}

font.customParameters['Axes'] = fontAxes

# this Python API approach also doesn't quite work :/

Is there something extra that must be done to set an Axes custom parameter in a font and have it take effect?