diff --git a/docs/latest/advanced/custom-tools.md b/docs/latest/advanced/custom-tools.md
index 399b04c8b..bed6c344f 100644
--- a/docs/latest/advanced/custom-tools.md
+++ b/docs/latest/advanced/custom-tools.md
@@ -1 +1,8 @@
 # Tool Management
+
+This is not yet exposed in an easy/convenient way. Most tools are currently
+added by creating new Viewport, Toolbar, and SOPInstanceHandler extension
+modules. You can read more about that approach in [extensions](./extensions.md).
+
+In the near future, we intend to improve the extensibility of tools for existing
+Viewports (like our Cornerstone.js and VTK.js viewports).