diff --git a/doc/ext/README.md b/doc/ext/README.md
new file mode 100644
index 0000000..d781fb3
--- /dev/null
+++ b/doc/ext/README.md
@@ -0,0 +1,18 @@
+# soju IRC extensions
+
+This directory documents various soju-specific IRC extensions. All of the
+extensions are under the vendored `soju.im` namespace.
+
+Introducing a vendored extension is a good way to experiment with new ideas and
+do some field testing. If a vendored extension is successful, please open a pull
+request on the [IRCv3 specifications] repository for standardization.
+
+## License
+
+All of the specifications in this directory are dual-licensed under the terms of
+the AGPLv3, or the following terms, at your discretion:
+
+> Unlimited redistribution and modification of this document is allowed provided
+> that the above copyright notice and this permission notice remains intact.
+
+[IRCv3 specifications]: https://github.com/ircv3/ircv3-specifications