diff --git a/examples/nn_text_class.py b/examples/nn_text_class.py
index e19e93cac..7b4a2fd57 100644
--- a/examples/nn_text_class.py
+++ b/examples/nn_text_class.py
@@ -1,3 +1,11 @@
+"""This script expects something like a binary sentiment data set, such as
+ that available here: `http://www.cs.cornell.edu/people/pabo/movie-review-data/`
+
+It expects a directory structure like: `data_dir/train/{pos|neg}`
+ and `data_dir/test/{pos|neg}`. Put (say) 90% of the files in the former
+ and the remainder in the latter.
+"""
+
 from __future__ import unicode_literals
 from __future__ import print_function
 from __future__ import division