diff --git a/.gitignore b/.gitignore
index 844902a..4e1c4bd 100644
--- a/.gitignore
+++ b/.gitignore
@@ -9,6 +9,8 @@ coverage
 
 # documentation
 rdoc
+doc
+.yardoc/
 
 # Temporary files
 .DS_Store
diff --git a/Gemfile b/Gemfile
index eef57cc..93cf7e2 100644
--- a/Gemfile
+++ b/Gemfile
@@ -18,6 +18,9 @@ group :development do
   gem "pry"
   gem "pry-debundle"
   gem "pry-byebug"
+
+  # documentation
+  gem "yard", require: false
 end
 
 group :test do
diff --git a/Gemfile.lock b/Gemfile.lock
index d81f370..5d8068b 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -186,6 +186,7 @@ GEM
       thread_safe (~> 0.1)
     uuid (2.3.8)
       macaddr (~> 1.0)
+    yard (0.8.7.6)
 
 PLATFORMS
   ruby
@@ -208,6 +209,7 @@ DEPENDENCIES
   simplecov-rcov (= 0.2.3)
   sqlite3
   uuid (= 2.3.8)
+  yard
 
 BUNDLED WITH
    1.10.3