Correct documentation on url_for. It doesn't call to_s, but rather to_param

actionpack/lib/action_view/helpers/url_helper.rb

@@ -81,9 +81,12 @@ module ActionView
       #   # => /workshops
       #
       #   <%= url_for(@workshop) %>
-      #   # calls @workshop.to_s
+      #   # calls @workshop.to_param which by default returns the id
       #   # => /workshops/5
       #
+      #   # to_param can be re-defined in a model to provide different URL names:
+      #   # => /workshops/1-workshop-name
+      #
       #   <%= url_for("http://www.example.com") %>
       #   # => http://www.example.com
       #