Font weights

To set the font weights :

{
	"settings": {
		"typography": {
			"fontFamilies": [
				{
					"fontFamily": "\"Barlow\", sans-serif",
					"name": "Barlow",
					"slug": "barlow",
					"fontFace" : [
						{
							"fontFamily": "Barlow",
							"fontWeight": "400",
							"src": "file:./assets/fonts/Barlow-Regular-webfont.woff"
						},
						{
							"fontFamily": "Barlow",
							"fontWeight": "500",
							"fontStyle": "normal",
							"src": "file:./assets/fonts/Barlow-Medium-webfont.woff"
						},
						{
							"fontFamily": "Barlow",
							"fontWeight": "700",
							"fontStyle": "normal",
							"src": "file:./assets/fonts/Barlow-Bold-webfont.woff"
						}
					]
				}
			]
		}
	}
}

Note : reduce a variable font to the required variations: fonttools varLib.instancer ./MyAwesomeVariableFont.ttf wdth=drop opsz=drop wght=300:700

https://morgan.cugerone.com/blog/how-to-disable-variable-fonts-variation-features-with-open-source-solution