diff --git a/mods/MAPGEN/mcl_structures/API.md b/mods/MAPGEN/mcl_structures/API.md
index 23d93c712a..ea051603fc 100644
--- a/mods/MAPGEN/mcl_structures/API.md
+++ b/mods/MAPGEN/mcl_structures/API.md
@@ -12,13 +12,19 @@ If nospawn is truthy the structure will not be placed by mapgen and the decorati
 	y_max =,
 	place_on = {},
 	spawn_by = {},
-	num_spawn_by =
+	num_spawn_by =,
 	flags = (default: "place_center_x, place_center_z, force_placement")
 	(same as decoration def)
-	y_offset =, --can be a number or a function returning a number
+	y_offset =, 	--can be a number or a function returning a number
 	filenames = {} OR place_func = function(pos,def,pr)
-	-- filenames can be a list of any schematics accepted by mcl_structures.place_schematic / minetest.place_schematic
+					-- filenames can be a list of any schematics accepted by mcl_structures.place_schematic / minetest.place_schematic
+	on_place = function(pos,def,pr) end,
+					-- called before placement. denies placement when returning falsy.
 	after_place = function(pos,def,pr)
+					-- executed after successful placement
+	sidelen = int, --length of one side of the structure. used for foundations.
+	solid_ground = bool, -- structure requires solid ground
+	make_foundation = bool, -- a foundation is automatically built for the structure. needs the sidelen param
 }
 ## mcl_structures.registered_structures
 Table of the registered structure defintions indexed by name.