diff --git a/lib/generators/categoria/data_generator.rb b/lib/generators/categoria/data_generator.rb
index e379f2a..f48de7e 100644
--- a/lib/generators/categoria/data_generator.rb
+++ b/lib/generators/categoria/data_generator.rb
@@ -7,6 +7,12 @@ class DataGenerator < ::Rails::Generators::NamedBase
       extend T::Sig
 
       source_root File.expand_path("templates", __dir__)
+
+      desc <<~DOC.squish
+        generates a data class for the domain. data classes are used
+        like value classes: hashes are more fit for the purpose except
+        that in the wild hashes are difficult to tame.
+      DOC
     end
   end
 end
diff --git a/lib/generators/categoria/templates/data.rb.erb b/lib/generators/categoria/templates/data.rb.erb
index e69de29..cea8572 100644
--- a/lib/generators/categoria/templates/data.rb.erb
+++ b/lib/generators/categoria/templates/data.rb.erb
@@ -0,0 +1,11 @@
+# frozen_string_literal: true
+
+module <%= Rails.application.class.module_parent %>
+  module <%= domain_module %>
+    module Data
+      class <%= data_class_name %> < ::Categoria::Data
+      end
+    end
+  end
+end
+