diff --git a/src/depot_type.h b/src/depot_type.h
--- a/src/depot_type.h
+++ b/src/depot_type.h
@@ -12,7 +12,7 @@
 #ifndef DEPOT_TYPE_H
 #define DEPOT_TYPE_H
 
-typedef uint16 DepotID;
+typedef uint16 DepotID; ///< Type for the unique identifier of depots.
 struct Depot;
 
 static const uint MAX_LENGTH_DEPOT_NAME_CHARS = 32; ///< The maximum length of a depot name in characters including '\0'