diff --git a/design/protocol.md b/design/protocol.md
index a9a4db8..f1a107e 100644
--- a/design/protocol.md
+++ b/design/protocol.md
@@ -46,6 +46,10 @@ bits, and the CN is 5 bits. Both are interpreted as unsigned integers. Both
 sides of the connection must agree on the semantic meaning of the values and
 their arrangement.
 
+A TAPE structure begins with one root, which consists of a tag followed by a
+payload. This is usually an aggregate data structure such as KTV to allow for
+several different values.
+
 TAPE is based on an encoding method previously developed by silt.
 
 ### Data Value Types