Simple example of an entity type description file for Screwdriver (shown in my blog). The beginning for a hypothetical full remake of Spacewalk.

spacewalk.lua

entityTypes["levelGeometry"] = {
	label = "Level geometry",
	components = {
		{
			id = "core", 
			componentType = "Core", -- every entity type has to have a core component
		},
		{	
			id = "transforms",
			componentType = "Transforms",
		},
		{
			id = "polygon",
			componentType = "BorderedFannedPolygon",
		}
	}
}

entityTypes["spawnZone"] = {
    label = "Spawn zone",
    components = {
		{
			id = "core",
			componentType = "Core",
		},
		{	
			id = "transforms",
			componentType = "Transforms",
		},
		{
			id = "polygon",
			componentType = "SimplePolygon",
		}
	}
}

entityTypes["weaponPod"] = {
	label = "Sprite + Transforms",
	components = {
		{
			id = "core",
			componentType = "Core",
		},
		{	
			id = "transforms",
			componentType = "Transforms",
		},
		{
			id = "sprite",
			componentType = "Sprite",
			imagePath = "pod.png"
		},
        {
            id = "weaponType",
            componentType = "MetadataChoice", -- other metadata components are available too (string, number, boolean, entity)
            choices = { -- id - label pairs
                rifle = "Rifle",
                shotgung = "Shotgun",
            },
            value = "rifle",
        }
	}
}