diff --git a/lib/hydra/hash.rb b/lib/hydra/hash.rb
index 0358141..4d445e0 100644
--- a/lib/hydra/hash.rb
+++ b/lib/hydra/hash.rb
@@ -1,10 +1,12 @@
 class Hash
+  # Stringify the keys in the hash. Returns a new hash.
   def stringify_keys
     inject({}) do |options, (key, value)|
       options[key.to_s] = value
       options
     end
   end
+  # Stringify the keys in the hash in place.
   def stringify_keys!
    keys.each do |key|
      self[key.to_s] = delete(key)