diff --git a/api.txt b/api.txt
index 436e7da..fe8ac6a 100644
--- a/api.txt
+++ b/api.txt
@@ -62,6 +62,10 @@ The stairs API lets you register stairs and slabs and ensures that they are regi
  * `sounds`: See [#Default sounds]
  * `worldaligntex`: A bool to set all textures world-aligned. Default false. See [Tile definition]
 
+`stairs.register_slope_outer(subname, recipeitem, groups, images, description, sounds, worldaligntex)`
+
+`stairs.register_slope_inner(subname, recipeitem, groups, images, description, sounds, worldaligntex)`
+
 
 `stairs.register_stair_and_slab(subname, recipeitem, groups, images, desc_stair, desc_slab, sounds, worldaligntex)`