diff --git a/api.txt b/api.txt
new file mode 100644
index 0000000..8e5c175
--- /dev/null
+++ b/api.txt
@@ -0,0 +1,9 @@
+
+Toggling Invisibility
+---------------------
+
+Any 3rd party mods can use the invisibility.invisible function to hide a player, but only
+the potion itself adds a timer to the function with a 10 second warning before becoming
+visible once again e.g.
+
+invisibility.invisible(player, [true for invisible, false for visible])
diff --git a/init.lua b/init.lua
index 855fb31..57776e8 100644
--- a/init.lua
+++ b/init.lua
@@ -24,7 +24,7 @@ end
 
 -- invisibility function
 
-local function invisible(player, toggle)
+function invisibility.invisible(player, toggle)
 
 	if not player then return false end
 
@@ -63,10 +63,7 @@ minetest.register_node("invisibility:potion", {
 	paramtype = "light",
 	is_ground_content = false,
 	walkable = false,
-	selection_box = {
-		type = "fixed",
-		fixed = {-0.25, -0.5, -0.25, 0.25, 0.3, 0.25}
-	},
+	selection_box = {type = "fixed", fixed = {-0.25, -0.5, -0.25, 0.25, 0.3, 0.25}},
 	groups = {vessel = 1, dig_immediate = 3, attached_node = 1},
 	sounds = default.node_sound_glass_defaults(),
 
@@ -84,7 +81,7 @@ minetest.register_node("invisibility:potion", {
 		end
 
 		-- make player invisible
-		invisible(user, true)
+		invisibility.invisible(user, true)
 
 		-- play sound
 		minetest.sound_play("pop", {
@@ -106,7 +103,7 @@ minetest.register_node("invisibility:potion", {
 			if invisibility[name] and user:get_pos() then
 
 				-- show hidden player
-				invisible(user, nil)
+				invisibility.invisible(user, nil)
 
 				-- play sound
 				minetest.sound_play("pop", {
@@ -179,9 +176,9 @@ minetest.register_chatcommand("vanish", {
 		-- hide / show player
 		if invisibility[name] then
 
-			invisible(player, nil)
+			invisibility.invisible(player, nil)
 		else
-			invisible(player, true)
+			invisibility.invisible(player, true)
 		end
 	end
 })
diff --git a/mod.conf b/mod.conf
index 4e44c2b..37fb043 100644
--- a/mod.conf
+++ b/mod.conf
@@ -1,4 +1,5 @@
 name = invisibility
 description = Craft a potion to make yourself invisible.
 depends = default
+optional_depends = flowers, vessels
 min_minetest_version = 5.0