fonttools · arrowtype · Sep 16, 2025 · Sep 16, 2025 · Sep 17, 2025 · Sep 17, 2025
diff --git a/Doc/source/designspaceLib/index.rst b/Doc/source/designspaceLib/index.rst
@@ -113,12 +113,28 @@ Common Lib Key Registry
 public.skipExportGlyphs
 -----------------------
 
-This lib key works the same as the UFO lib key with the same name. The
-difference is that applications using a Designspace as the corner stone of the
-font compilation process should use the lib key in that Designspace instead of
-any of the UFOs. If the lib key is empty or not present in the Designspace, all
-glyphs should be exported, regardless of what the same lib key in any of the
-UFOs says.
+This lib key works the same as the UFO lib key with the same name.
+
+With a hierarchy similar to 
+`public.fontInfo <https://fonttools.readthedocs.io/en/stable/designspaceLib/index.html#public-fontinfo>`, 
+``public.skipExportGlyphs`` should be inherited using the following order, in 
+order of descending priority:
+
+#. The ``public.skipExportGlyphs`` key in the ``<lib>`` element of the
+   ``<variable-font>`` or ``<instance>`` elements.
+#. The ``public.skipExportGlyphs`` key found in the ``<lib>`` element of the
+   designspace document’s root.
+#. The ``lib.plist`` in the UFO source at the origin of the interpolation space.
+
+To give examples:
+-  If the lib key is defined in ``<variable-font>`` or ``<instance>`` elements,
+   it should be applied to each of those outputs specifically.
+-  If the lib key is present but empty in the Designspace, all glyphs should be
+   exported, regardless of what the same lib key in any of the UFOs says.
+-  If the lib key is not present in the Designspace but it is present in the
+   default source of the Designspace, the font compiler should use the lib key 
+   from that UFO, and it should apply that set of skipped glyphs to any fonts 
+   compiled from the Designspace.
 
 public.fontInfo
 -----------------------

diff --git a/Lib/fontTools/designspaceLib/__init__.py b/Lib/fontTools/designspaceLib/__init__.py
@@ -2729,6 +2729,9 @@ def __init__(self, readerClass=None, writerClass=None):
 
         Use reverse-DNS notation to identify your own data.
         Respect the data stored by others.
+
+        For common keys and their inheritance behavior, see:
+        `Common Lib Key Registry <https://fonttools.readthedocs.io/en/latest/designspaceLib/index.html#common-lib-key-registry>`_
         """
 
         self.default: Optional[str] = None