diff --git a/Marlin/Version.h b/Marlin/Version.h
index 33a9260f47..63f4b81ab8 100644
--- a/Marlin/Version.h
+++ b/Marlin/Version.h
@@ -61,7 +61,9 @@
   #define REQUIRED_CONFIGURATION_ADV_H_VERSION 010100
 
   /**
-   * @todo: Missing documentation block
+   * The protocol for communication to the host. Protocol indicates communication
+   * standards such as the use of ASCII, "echo:" and "error:" line prefixes, etc.
+   * (Other behaviors are given by the firmware version and capabilities report.)
    */
   #define PROTOCOL_VERSION "1.0"