diff --git a/doc/usage.md b/doc/usage.md
index 4990950..e4c854c 100644
--- a/doc/usage.md
+++ b/doc/usage.md
@@ -293,3 +293,4 @@ while :; do git diff HEAD --; sleep 5; done | tee >(o myproj/security write feed
 
 For technical details on the raw 9P filesystem, see [`doc/9p.md`](9p.md).
 For tool authoring, see [`doc/writing-tools.md`](writing-tools.md).
+For meta-only tool definitions (no script needed), see [`doc/tool-definitions.md`](tool-definitions.md).