diff --git a/main.go b/main.go
index b081d8c05..019278b7f 100644
--- a/main.go
+++ b/main.go
@@ -1,3 +1,11 @@
+// mtg is just a command-line application that starts a proxy.
+//
+// Application logic is how to read a config and configure mtglib.Proxy.
+// So, probably you need to read the documentation for mtglib package
+// first.
+//
+// mtglib is a core of the application. The rest of the packages provide
+// some default implementations for the interfaces, defined in mtglib.
 package main
 
 import (