diff --git a/doc/README.md b/doc/README.md
index a0f050ecd5cfc8..3d8ad6246839e6 100644
--- a/doc/README.md
+++ b/doc/README.md
@@ -35,6 +35,8 @@ this guide.
   (`[a link](http://example.com)`).
 * When documenting APIs, update the YAML comment associated with the API as
   appropriate. This is especially true when introducing or deprecating an API.
+* When documenting APIs, every function should have a usage example or
+  link to an example that uses the function.
 * For code blocks:
   * Use [language][]-aware fences. (<code>\`\`\`js</code>)