diff --git a/src/skills/nix-style/SKILL.md b/src/skills/nix-style/SKILL.md
index ddba819..c7914c6 100644
--- a/src/skills/nix-style/SKILL.md
+++ b/src/skills/nix-style/SKILL.md
@@ -18,6 +18,11 @@ find src/skills/nix-style/rules -maxdepth 1 -type f -name '*.md' -print | sort
 
 Finish when all discovered rule files have been read.
 
+## Maintain rules
+
+When adding or changing files under [`rules/`](rules/), read [`RULE-FORMAT.md`](RULE-FORMAT.md) first.
+Finish when the changed rule files follow that format.
+
 ## Apply rules
 
 Apply the loaded rules when editing or reviewing Nix files.