diff --git a/init.lua b/init.lua
index 2470b57..c65b68c 100644
--- a/init.lua
+++ b/init.lua
@@ -4,17 +4,15 @@ local modpath = minetest.get_modpath("cartographer");
 -- Includes
 local map_data = loadfile(modpath .. "/storage.lua") ();
 local chunk = loadfile(modpath .. "/chunk_api.lua") ();
-local skin = loadfile(modpath .. "/skin_api.lua") ();
 local gui = loadfile(modpath .. "/formspec.lua") ();
-local audio = loadfile(modpath .. "/audio.lua") ();
+local skin = loadfile(modpath .. "/skin_api.lua") ();
 local util = loadfile(modpath .. "/util.lua") ();
-
+local audio = loadfile(modpath .. "/audio.lua") ();
 local biomes = loadfile(modpath .. "/biome_api.lua") (util);
-
+local markers = loadfile(modpath .. "/marker_api.lua") ();
 local scanner = loadfile(modpath .. "/scanner.lua") (map_data, chunk);
 local maps = loadfile(modpath .. "/map_api.lua") (map_data, chunk);
 local materials = loadfile(modpath .. "/material_api.lua") ();
-local markers = loadfile(modpath .. "/marker_api.lua") ();
 local map_formspec = loadfile(modpath .. "/map_formspec.lua") (map_data, gui, skin, util, biomes, markers);
 local map_item = loadfile(modpath .. "/items.lua") (chunk, gui, skin, audio, maps, markers, map_formspec);
 loadfile(modpath .. "/commands.lua") (chunk, audio, map_formspec);
diff --git a/items.lua b/items.lua
index 7c94c1a..ad05968 100644
--- a/items.lua
+++ b/items.lua
@@ -1,9 +1,18 @@
+-- Arguments
+-- chunk: The chunk coordinate conversion API
+-- gui: The GUI API
+-- skin: The GUI skin
+-- audio: The audio playback API
+-- maps: The map API
+-- markers: The marker API
+-- map_formspec: The map display API
 local chunk, gui, skin, audio, maps, markers, map_formspec = ...;
 
 -- The list of players looking at maps, and the map IDs that they're looking at
 local player_maps = {};
 
--- Generates formspec data for the map marker editor
+-- Generate formspec data for the map marker editor
+--
 -- selected_id: The id of the currently selected marker, or nil if no marker is
 --              selected
 -- detail: The map's detail level
@@ -90,23 +99,19 @@ local function marker_formspec(selected_id, detail, page)
     return table.concat(formspec);
 end
 
--- Show a map to a player from the ID
--- id: The map ID
+-- Show a map to a player
+--
+-- map: The map to display
 -- player_x: The X position (in world coordinates)
 -- player_z: The Z position (in world coordinates)
 -- player_name: The name of the player to show to
 -- height_mode: Whether or not to display the map in height mode
 -- (Optional) marker_page: The current page that the marker editor is on
-local function show_map_id_formspec(id, player_x, player_z, player_name, height_mode, marker_page)
-    local map = maps.get(id);
-    if not map then
-        return
-    end
-
-    map:fill_local(id, player_x, player_z);
+local function show_map_formspec(map, player_x, player_z, player_name, height_mode, marker_page)
+    map:fill_local(player_x, player_z);
 
     player_maps[player_name] = {
-        id = id,
+        id = map.id,
         page = marker_page or 1,
         height_mode = height_mode,
     };
@@ -174,11 +179,14 @@ local function show_map_id_formspec(id, player_x, player_z, player_name, height_
 end
 
 -- Get the description text for a map ID and dimensions
+--
 -- id: The map ID
 -- from_x: The x coordinate of the top-left corner of the map, in world coordinates
 -- from_z: The z coordinate of the top-left corner of the map, in world coordinates
 -- w: The width, in world coordinates
 -- h: The height, in world coordinates
+--
+-- returns a string containing the description
 local function map_description(id, from_x, from_z, w, h)
     return string.format("Map #%d\n[%d,%d] - [%d,%d]",
                          id,
@@ -187,9 +195,12 @@ local function map_description(id, from_x, from_z, w, h)
 end
 
 -- Create a map from metadata, and assign the ID to the metadata
+--
 -- meta: A metadata object containing the map ID
 -- player_x: The X position (in map coordinates)
 -- player_z: The Z position (in map coordinates)
+--
+-- Returns the id of the new map
 local function map_from_meta(meta, player_x, player_z)
     local size = meta:get_int("cartographer:size") or 10;
     local detail = meta:get_int("cartographer:detail") or 1;
@@ -208,7 +219,8 @@ local function map_from_meta(meta, player_x, player_z)
     return id;
 end
 
--- Show a map to a player from metadata, creating it if possible
+-- Show a map to a player from metadata, creating it if necessary
+--
 -- meta: A metadata object containing the map ID
 -- player: The player to show the map to
 local function show_map_meta(meta, player)
@@ -221,11 +233,15 @@ local function show_map_meta(meta, player)
         id = map_from_meta(meta, player_x, player_z);
     end
 
-    show_map_id_formspec(id, pos.x, pos.z, player:get_player_name(), true);
+    local map = maps.get(id);
+    if map then
+        show_map_formspec(map, pos.x, pos.z, player:get_player_name(), true);
+    end
 end
 
 -- Called when a player sends input to the server from a formspec
 -- This callback handles player input in the map formspec, for editing markers
+--
 -- player: The player who sent the input
 -- name: The formspec name
 -- fields: A table containing the input
@@ -249,13 +265,13 @@ minetest.register_on_player_receive_fields(function(player, name, fields)
                 map:set_marker(player_x, player_z, marker);
 
                 audio.play_feedback("cartographer_write", player);
-                show_map_id_formspec(map.id, pos.x, pos.z, player:get_player_name(), data.page);
+                show_map_formspec(map, pos.x, pos.z, player:get_player_name(), data.page);
             elseif k == "prev_button" then
-                show_map_id_formspec(map.id, pos.x, pos.z, player:get_player_name(), data.height_mode, data.page - 1);
+                show_map_formspec(map, pos.x, pos.z, player:get_player_name(), data.height_mode, data.page - 1);
             elseif k == "next_button" then
-                show_map_id_formspec(map.id, pos.x, pos.z, player:get_player_name(), data.height_mode, data.page + 1);
+                show_map_formspec(map, pos.x, pos.z, player:get_player_name(), data.height_mode, data.page + 1);
             elseif k == "height_button" then
-                show_map_id_formspec(map.id, pos.x, pos.z, player:get_player_name(), not data.height_mode, data.page);
+                show_map_formspec(map, pos.x, pos.z, player:get_player_name(), not data.height_mode, data.page);
             elseif k == "quit" then
                 player_maps[player:get_player_name()] = nil;
             end
@@ -345,6 +361,13 @@ minetest.register_node("cartographer:map", {
     end,
 });
 
+-- Create an empty map item with the given parameters
+--
+-- size: The size of the map
+-- detail: The detail level of the map
+-- scale: The scaling factor of the map
+--
+-- Returns an ItemStack
 local function create_map_item(size, detail, scale)
     local map = ItemStack("cartographer:map");
     local meta = map:get_meta();
@@ -357,9 +380,10 @@ local function create_map_item(size, detail, scale)
 end
 
 -- Create a copy of the given map
+--
 -- stack: An itemstack containing a map
 --
--- Returns an itemstack with the copied map
+-- Returns a new ItemStack with the copied map
 local function copy_map_item(stack)
     local meta = stack:get_meta();
 
@@ -392,6 +416,10 @@ local function copy_map_item(stack)
     return copy;
 end
 
+-- Resize the given map item
+--
+-- meta: A metadata object containing the map data
+-- size: The new size
 local function resize_map_item(meta, size)
     local old_size = meta:get_int("cartographer:size");
 
@@ -407,8 +435,8 @@ local function resize_map_item(meta, size)
         map:resize(size, size);
 
         meta:set_string("description", map_description(id,
-                                                            chunk.from(map.x), chunk.from(map.z),
-                                                            chunk.from(map.w), chunk.from(map.h)));
+                                                       chunk.from(map.x), chunk.from(map.z),
+                                                       chunk.from(map.w), chunk.from(map.h)));
     end
 end
 
diff --git a/map_api.lua b/map_api.lua
index 6990d03..43cdc55 100644
--- a/map_api.lua
+++ b/map_api.lua
@@ -1,5 +1,9 @@
+-- Arguments
+-- map_data: The map data source
+-- chunk: The chunk coordinate conversion API
 local map_data, chunk = ...;
 
+-- The map 'class'
 local Map = {};
 Map.__index = Map;
 
@@ -7,6 +11,10 @@ for _,loaded_map in ipairs(map_data.maps) do
     setmetatable(loaded_map, Map);
 end
 
+-- Resize this map
+--
+-- w: The new width
+-- h: The new height
 function Map.resize(self, w, h)
     if w >= self.w and h >= self.h then
         self.w = w;
@@ -15,6 +23,13 @@ function Map.resize(self, w, h)
     end
 end
 
+
+-- Fill in a region of this map
+--
+-- x: The x position, in map coordinates
+-- z: The z position, in map coordinates
+-- w: The width, in map coordinates
+-- h: The height, in map coordinates
 function Map.fill_area(self, x, z, w, h)
     for i = math.max(x, self.x),math.min(x + w - 1, self.x + self.w),1 do
         for j = math.max(z, self.z),math.min(z + h - 1, self.z + self.h),1 do
@@ -23,6 +38,11 @@ function Map.fill_area(self, x, z, w, h)
     end
 end
 
+-- Set the marker at the given position
+--
+-- x: The x position, in map coordinates
+-- z: The z position, in map coordinates
+-- marker: The marker ID to set, or nil to unset
 function Map.set_marker(self, x, z, marker)
     if x < self.x or x > self.x + self.w or z < self.z or z > self.z + self.h then
         return;
@@ -37,6 +57,12 @@ function Map.set_marker(self, x, z, marker)
     end
 end
 
+-- Get the marker at the given position
+--
+-- x: The x position, in map coordinates
+-- z: The z position, in map coordinates
+--
+-- Returns a marker id
 function Map.get_marker(self, x, z)
     if x < self.x or x > self.x + self.w or z < self.z or z > self.z + self.h or not self.markers[x] then
         return nil;
@@ -46,6 +72,7 @@ function Map.get_marker(self, x, z)
 end
 
 -- Fill in the local area of a map around a position
+--
 -- id: A map ID
 -- x: The x position, in world coordinates
 -- z: The z position, in world coordinates
@@ -59,7 +86,7 @@ function Map.fill_local(self, x, z)
 end
 
 -- Convert a position in world coordinates to the given map's coordinate system
--- self: The map to use as reference
+--
 -- x: The x position, in world coordinates
 -- z: The z position, in world coordinates
 --
@@ -72,11 +99,27 @@ function Map.to_coordinates(self, x, z)
     return math.floor(chunk.to(x) / self.scale + 0.5), math.floor(chunk.to(z) / self.scale + 0.5);
 end
 
+-- Check if the given position on this map is filled
+--
+-- x: The x position, in map coordinates
+-- z: The z position, in map coordinates
 function Map.is_filled(self, x, z)
     return self.fill[(x - self.x) + ((z - self.z) * self.w)] ~= nil;
 end
 
+-- The Map API
 local maps = {
+    -- Create a new map object with the given parameters
+    --
+    -- x: The x position, in map coordinates
+    -- z: The z position, in map coordinates
+    -- w: The width, in map coordinates
+    -- h: The height, in map coordinates
+    -- filled: Whether or not the map is pre-filled
+    -- detail: The detail level
+    -- scale: The scale factor
+    --
+    -- Returns the new map's id
     create = function(x, z, w, h, filled, detail, scale)
         local id = map_data.next_map_id;
 
@@ -103,6 +146,11 @@ local maps = {
         return id;
     end,
 
+    -- Get the map objwct assigned to the given id
+    --
+    -- id: The map id
+    --
+    -- Returns a map object, or nil if the id is invalid
     get = function(id)
         return map_data.maps[id];
     end,
diff --git a/map_formspec.lua b/map_formspec.lua
index d7ef870..bd48ff6 100644
--- a/map_formspec.lua
+++ b/map_formspec.lua
@@ -1,5 +1,10 @@
 -- Arguments
 -- map_data: The cartographer map data table
+-- gui: The GUI API
+-- skin: The GUI skin
+-- util: API for uncategorized utility methods
+-- biomes: The biome API
+-- markers: The marker API
 local map_data, gui, skin, util, biomes, markers = ...;
 
 -- Constants
diff --git a/marker_api.lua b/marker_api.lua
index 05ce59c..519228d 100644
--- a/marker_api.lua
+++ b/marker_api.lua
@@ -3,6 +3,7 @@ local marker_lookup = {};
 -- Format marker ids to allow their use as formspec element ids.
 -- We're mostly concerned with guarding against the : character because it is
 -- common for ids and has an alternate meaning in formspecs.
+--
 -- id: The id to format
 --
 -- Returns the formatted id
@@ -11,6 +12,7 @@ local function format_marker_id(id)
 end
 
 -- Find the marker data for a given id
+--
 -- id: The id to search for
 --
 -- Returns the marker data, or nil if not found
@@ -44,6 +46,7 @@ local function get_registered_markers()
 end
 
 -- Register a marker with textures to display
+--
 -- id: A string containing the id of the marker
 -- name: A string containing the displayedname of the marker
 -- textures: A table of texture names.
@@ -69,6 +72,7 @@ local function add_marker(id, name, textures)
 end
 
 -- Get the texture name (minus extension) for the given marker and detail level.
+--
 -- id: A string containing the marker id
 -- detail: The detail level
 -- Returns a string with a texture name, or nil if no matching marker was found.
diff --git a/material_api.lua b/material_api.lua
index c3a855d..76c1a32 100644
--- a/material_api.lua
+++ b/material_api.lua
@@ -3,6 +3,7 @@ local materials_by_group = {};
 
 return {
     -- Get the converted material value of the given itemstack
+    --
     -- stack: The itemstack to convert
     --
     -- Returns a table with the material values
@@ -34,6 +35,11 @@ return {
         };
     end,
 
+    -- Register a material from an item name
+    --
+    -- name: The name of the item
+    -- material: The material type to set
+    -- value: The material value
     register_by_name = function(name, material, value)
         if materials_by_name[name] then
             materials_by_name[name][material] = value or 1;
@@ -44,6 +50,11 @@ return {
         end
     end,
 
+    -- Register a material from an item group
+    --
+    -- group: The name of the group
+    -- material: The material type to set
+    -- value: The material value
     register_by_group = function(name, material, value)
         if materials_by_group[name] then
             materials_by_group[name][material] = value or 1;
diff --git a/mod.conf b/mod.conf
index 611eab3..b0dad78 100644
--- a/mod.conf
+++ b/mod.conf
@@ -1,2 +1,2 @@
 name = cartographer
-description = A game-agnostic mapmaking API. Needs additional mods to function.
+description = A mapmaking API. Needs additional mods to function.
diff --git a/scanner.lua b/scanner.lua
index 7e8746d..58b3fff 100644
--- a/scanner.lua
+++ b/scanner.lua
@@ -1,5 +1,6 @@
 -- Arguments
 -- map_data: The cartographer map data table
+-- chunk: The chunk coordinate conversion API
 local map_data, chunk = ...;
 
 local scan_queue = {};
@@ -34,6 +35,14 @@ local function register_tile(x, y, biome, height, manual_scan)
     end
 end
 
+-- Get the biome and height data for a region from mapgen data
+--
+-- min: The min coord of the generated terrain
+-- max: The max coord of the generated terrain
+-- mmin: The min coord of the region to scan
+-- mmax: The max coord of the region to scan
+--
+-- Returns the biome and height of the scanned region
 local function get_mapgen_biome(min, max, mmin, mmax)
     local UNDERGROUND = minetest.get_biome_id("underground");
     local DEFAULT = minetest.get_biome_id("default");
@@ -79,6 +88,12 @@ local function get_mapgen_biome(min, max, mmin, mmax)
     return biome, avg_height;
 end
 
+-- Get the biome and height data for a region from existing terrain
+--
+-- min: The min coord of the region to scan
+-- max: The max coord of the region to scan
+--
+-- Returns the biome and height of the scanned region
 local function get_biome(min, max)
     local UNDERGROUND = minetest.get_biome_id("underground");
     local DEFAULT = minetest.get_biome_id("default");
@@ -122,6 +137,10 @@ local function get_biome(min, max)
     return biome, avg_height;
 end
 
+-- Called when new terrain is generated
+--
+-- min: The min coord of the generated terrain
+-- max: The max coord of the generated terrain
 local function on_generated(min, max, _)
     for i = chunk.to(min.x),chunk.to(max.x),1 do
         for j = chunk.to(min.z),chunk.to(max.z),1 do
@@ -144,10 +163,10 @@ local function on_generated(min, max, _)
         end
     end
 end
-
 minetest.register_on_generated(on_generated);
 
 -- Is the scan of this position already handled?
+--
 -- x: The x position, in map coordinates
 -- y: The y position, in world coordinates
 -- x: The z position, in map coordinates
@@ -166,6 +185,7 @@ end
 local scanner = {};
 
 -- Queue a tile for manual scanning
+--
 -- pos: The position as a table, in world coordinates
 function scanner.queue_region(pos)
     local converted = {
diff --git a/skin_api.lua b/skin_api.lua
index f03f5b5..1722ce8 100644
--- a/skin_api.lua
+++ b/skin_api.lua
@@ -178,6 +178,9 @@ return {
         radius = 8,
     },
 
+    -- The texture of the height toggle button when active
     height_button_texture = "cartographer_height_button",
+
+    -- The texture of the height toggle button when inactive
     flat_button_texture = "cartographer_flat_button",
 };
diff --git a/storage.lua b/storage.lua
index 7f498b6..c764f89 100644
--- a/storage.lua
+++ b/storage.lua
@@ -1,20 +1,32 @@
 -- Storage and saving
 local mod_storage = minetest.get_mod_storage();
 local map_data = {
+    -- Scanned map data
     generated = minetest.deserialize(mod_storage:get_string("map")) or {},
 
+    -- Maps
     maps = minetest.deserialize(mod_storage:get_string("maps")) or {},
+
+    -- The next id
     next_map_id = mod_storage:get_int("next_map_id"),
+
+    -- The version of the map api
+    api_version = mod_storage:get_int("api_version"),
 };
 
 if map_data.next_map_id == 0 then
     map_data.next_map_id = 1;
 end
 
+if map_data.api_version == 0 then
+    map_data.api_version = 1;
+end
+
 local function save()
     mod_storage:set_string("maps", minetest.serialize(map_data.maps));
     mod_storage:set_int("next_map_id", map_data.next_map_id);
     mod_storage:set_string("map", minetest.serialize(map_data.generated));
+    mod_storage:set_string("api_version", minetest.serialize(map_data.api_version));
 end
 minetest.register_on_shutdown(save);
 minetest.register_on_leaveplayer(save);