diff --git a/betterproto-extras/betterproto_extras.pyi b/betterproto-extras/betterproto_extras.pyi
new file mode 100644
index 0000000..1741626
--- /dev/null
+++ b/betterproto-extras/betterproto_extras.pyi
@@ -0,0 +1,5 @@
+def deserialize(msg, data: bytes):
+    """
+    Parses the binary encoded Protobuf `data` with respect to the metadata
+    given by the betterproto message `msg`, and merges the result into `msg`.
+    """
\ No newline at end of file