diff --git a/CONTRIBUTING b/CONTRIBUTING
index d7fdc8e..b7ad7a8 100644
--- a/CONTRIBUTING
+++ b/CONTRIBUTING
@@ -97,9 +97,10 @@ their editor or terminal.
 
 For usage text and help messages, do not implement a -h option. Instead, print
 usage information when any erroneous option is specified. Follow the NetBSD
-style guide for the usage text’s output format [1].
+style guide for the usage text’s output format [0].
 
-[1] <http://cvsweb.netbsd.org/bsdweb.cgi/~checkout~/src/share/misc/style>
+If committing a new utility, please include tests and documentation (see
+tests/ and docs/) for the new tool.
 
 If committing a new source file, format the commit message following these
 guidelines:
@@ -128,6 +129,7 @@ $ git commit -m 'tool(1): fix #42 & add feature x'
 
 Commit messages should be written in the present tense.
 
+[0] <http://cvsweb.netbsd.org/bsdweb.cgi/~checkout~/src/share/misc/style>
 --
 This work © 2023–2024 by Emma Tebibyte is licensed under CC BY-SA 4.0. To view a
 copy of this license, visit <http://creativecommons.org/licenses/by-sa/4.0/>