diff --git a/lib/architex/schema/room.ex b/lib/architex/schema/room.ex
index 85a14e2..c27a88f 100644
--- a/lib/architex/schema/room.ex
+++ b/lib/architex/schema/room.ex
@@ -68,8 +68,8 @@ defmodule Architex.Room do
     end
   end
 
+  @spec get_messages(Room.t(), Messages.t()) :: {[Event.t()], integer() | nil, integer() | nil}
   def get_messages(room, %Messages{from: from, to: to, dir: dir, limit: limit}) do
-    # TODO: Check 'from' and 'to' formats.
     limit = limit || 10
 
     events =
@@ -84,11 +84,13 @@ defmodule Architex.Room do
     {events, get_start(events, dir), get_end(events, limit, dir)}
   end
 
+  @spec order_by_direction(Ecto.Query.t(), String.t()) :: Ecto.Query.t()
   defp order_by_direction(query, "b"), do: order_by(query, desc: :origin_server_ts, desc: :nid)
   defp order_by_direction(query, "f"), do: order_by(query, asc: :origin_server_ts, asc: :nid)
 
   # When 'from' is empty, we return events from the start or end
   # of the room's history.
+  @spec events_from(Ecto.Query.t(), String.t(), String.t()) :: Ecto.Query.t()
   defp events_from(query, "", _), do: query
 
   defp events_from(query, from, "b") do
@@ -101,6 +103,7 @@ defmodule Architex.Room do
     where(query, [e], e.nid > ^from)
   end
 
+  @spec events_to(Ecto.Query.t(), String.t() | nil, String.t()) :: Ecto.Query.t()
   defp events_to(query, nil, _), do: query
 
   defp events_to(query, to, "b") do
@@ -113,8 +116,8 @@ defmodule Architex.Room do
     where(query, [e], e.nid <= ^to)
   end
 
+  @spec get_start([Event.t()], String.t()) :: integer() | nil
   defp get_start([], _), do: nil
-
   defp get_start([%Event{nid: first_nid} | _], "f"), do: first_nid
 
   defp get_start(events, "b") do
@@ -122,6 +125,7 @@ defmodule Architex.Room do
     last_nid
   end
 
+  @spec get_end([Event.t()], integer(), String.t()) :: integer() | nil
   defp get_end(events, limit, _) when length(events) < limit, do: nil
 
   defp get_end([%Event{nid: first_nid} | _], _, "f"), do: first_nid
diff --git a/lib/architex_web/client/controllers/room_controller.ex b/lib/architex_web/client/controllers/room_controller.ex
index 05e53fa..3a9b244 100644
--- a/lib/architex_web/client/controllers/room_controller.ex
+++ b/lib/architex_web/client/controllers/room_controller.ex
@@ -204,6 +204,11 @@ defmodule ArchitexWeb.Client.RoomController do
 
   def unban(conn, _), do: put_error(conn, :missing_param)
 
+  @doc """
+  This endpoint is used to send a message event to a room.
+
+  Action for PUT /_matrix/client/r0/rooms/{roomId}/send/{eventType}/{txnId}.
+  """
   def send_message(
         %Conn{assigns: %{account: account, device: device}, body_params: body_params} = conn,
         %{
@@ -229,6 +234,11 @@ defmodule ArchitexWeb.Client.RoomController do
     end
   end
 
+  @doc """
+  This API returns a list of message and state events for a room.
+
+  Action for GET /_matrix/client/r0/rooms/{roomId}/messages.
+  """
   def messages(%Conn{assigns: %{account: account}} = conn, %{"room_id" => room_id} = params) do
     with {:ok, request} <- Messages.parse(params) do
       room_query =
diff --git a/lib/architex_web/client/request/messages.ex b/lib/architex_web/client/request/messages.ex
index b103365..e6b80d9 100644
--- a/lib/architex_web/client/request/messages.ex
+++ b/lib/architex_web/client/request/messages.ex
@@ -1,6 +1,14 @@
 defmodule ArchitexWeb.Client.Request.Messages do
   use ArchitexWeb.Request
 
+  @type t :: %__MODULE__{
+    from: String.t(),
+    to: String.t() | nil,
+    dir: String.t(),
+    limit: integer() | nil,
+    filter: String.t() | nil
+  }
+
   @primary_key false
   embedded_schema do
     field :from, :string