Luminance Mask type in REST API

I’m using Figma REST API for exporting project. How do I know if I use Luminance Mask type. In REST API we only have IsMask and IsMaskOutline properties, that can cover Alpha and Vector Mask Types.

This should now be available in the REST API through the maskType property, which gives the same values as the plugin API. The documentation for this should come out tomorrow Oct 18.