diff --git a/category-cycles/README.md b/category-cycles/README.md
new file mode 100644
index 0000000..6486749
--- /dev/null
+++ b/category-cycles/README.md
@@ -0,0 +1,12 @@
+## Category cycles
+
+Used to generate [User:SDZeroBot/Category_cycles](https://en.wikipedia.org/wiki/User:SDZeroBot/Category_cycles). 
+
+Run using `bash run.sh`.
+
+Files:
+- get_edges.sql: Get a list of all parentcat—subcat connections through the database, with only the category page IDs for efficiency in the next step.
+- find_cycles.cpp: Use depth-first search in the graph to detect the cycles.
+- prettify.js: Translate the page IDs to titles using the API, and publish report to wiki.
+
+[phab:T263096](https://phabricator.wikimedia.org/T263096) seeks to make such a script a part of MediaWiki.