diff --git a/tools/build/stale-symlink-buildworld.sh b/tools/build/stale-symlink-buildworld.sh
index 32ebc1f9d66d..acc3fb0baaf2 100755
--- a/tools/build/stale-symlink-buildworld.sh
+++ b/tools/build/stale-symlink-buildworld.sh
@@ -1,55 +1,64 @@
 #!/bin/sh
 # Copyright (c) Feb 2024 Wolfram Schneider <wosch@FreeBSD.org>
 # SPDX-License-Identifier: BSD-2-Clause
 #
 # stale-symlink-buildworld.sh - check for stale symlinks on a FreeBSD system
 #
-# You can run the script before or after `make installworld'
+# The purpose of this script is to detect stale symlinks, report them to
+# stderr and exit with a non-zero status. All other cases are ignored,
+# such as no symlinks, missing directories, permission problems, etc.
 #
+# You can run the script before or after `make installworld', or any other
+# make targets thats installs files.
+#
+# You can also check your local ports with:
+#    
+#   env STALE_SYMLINK_BUILDWORLD_DIRS=/usr/local ./stale-symlink-buildworld.sh
+
 
 PATH="/bin:/usr/bin"; export PATH
 
 : ${ncpu=$(nproc)}
 
 obj_dir_prefix=${MAKEOBJDIRPREFIX:="/usr/obj"}
 
 # check other directories as well
 : ${STALE_SYMLINK_BUILDWORLD_DIRS=$obj_dir_prefix}
 
 trap 'rm -f $script' 0
 script=$(mktemp -t stale-symlink)
 chmod u+x $script
 
 # create a temporary shell script to check for stale symbolic links
 cat << 'EOF' > $script
 file="$1"
 
 if [ ! -e "$file" ]; then
   echo "stale symlink detected: $(ls -ld $file)" >&2
   exit 1
 else
   exit 0
 fi
 EOF
 
 find -s -H \
   /bin \
   /boot \
   /etc \
   /lib \
   /libexec \
   /sbin \
   /usr/bin \
   /usr/include \
   /usr/lib \
   /usr/lib32 \
   /usr/libdata \
   /usr/libexec \
   /usr/sbin \
   /usr/src \
   /usr/share \
   $STALE_SYMLINK_BUILDWORLD_DIRS \
   -type l \
   -print0 | xargs -n1 -0 -P${ncpu} $script
 
 #EOF