diff --git a/tools/gen_cyglto_dll.sh b/tools/gen_cyglto_dll.sh
index 0633d1c..a855d46 100755
--- a/tools/gen_cyglto_dll.sh
+++ b/tools/gen_cyglto_dll.sh
@@ -1,4 +1,8 @@
 #!/usr/bin/env bash
+#
+# Build and install the LTO library, which the Cygwin package of
+# libLLVM is lacking.
+#
 
 pushd "${0%/*}/.." &>/dev/null
 source tools/tools.sh
diff --git a/tools/gen_sdk_package.sh b/tools/gen_sdk_package.sh
index c19abda..2f9d708 100755
--- a/tools/gen_sdk_package.sh
+++ b/tools/gen_sdk_package.sh
@@ -1,5 +1,7 @@
 #!/usr/bin/env bash
-# OS X SDK packaging script
+#
+# Package the OS X SDKs into a tar file to be used by `build.sh`.
+#
 
 export LC_ALL=C
 
diff --git a/tools/gen_sdk_package_darling_dmg.sh b/tools/gen_sdk_package_darling_dmg.sh
index 0de5756..5004a66 100755
--- a/tools/gen_sdk_package_darling_dmg.sh
+++ b/tools/gen_sdk_package_darling_dmg.sh
@@ -1,4 +1,13 @@
 #!/usr/bin/env bash
+#
+# Mount a Xcode .dmg (using fuse) and run gen_sdk_package.sh.
+#
+# Works up to Xcode 7.3
+#
+# This script uses darling-dmg and fuse to mount the .dmg, thus
+# avoiding to actually unpack it.
+# darling-dmg will be downloaded and compiled if missing.
+#
 
 pushd "${0%/*}/.." &>/dev/null
 source tools/tools.sh
diff --git a/tools/gen_sdk_package_p7zip.sh b/tools/gen_sdk_package_p7zip.sh
index 1f50167..9121222 100755
--- a/tools/gen_sdk_package_p7zip.sh
+++ b/tools/gen_sdk_package_p7zip.sh
@@ -1,4 +1,12 @@
 #!/usr/bin/env bash
+#
+# Extract required files from a Xcode .dmg using p7zip and run
+# gen_sdk_package.sh.
+#
+# Works up to Xcode 7.2
+#
+# p7zip will be downloaded and compiled if missing.
+#
 
 pushd "${0%/*}/.." &>/dev/null
 source tools/tools.sh
diff --git a/tools/mount_xcode_image.sh b/tools/mount_xcode_image.sh
index d234bad..30e2a7e 100755
--- a/tools/mount_xcode_image.sh
+++ b/tools/mount_xcode_image.sh
@@ -1,4 +1,9 @@
 #!/usr/bin/env bash
+#
+# Mount a Xcode .dmg (requires root) and run gen_sdk_package.sh.
+#
+# Works up to Xcode 4.2
+#
 
 if [ $(uname -s) != "Linux" ]; then
   echo "This script must be run on Linux"