diff --git a/go/vcs/vcs.go b/go/vcs/vcs.go
index 1c87793b9e..501c894254 100644
--- a/go/vcs/vcs.go
+++ b/go/vcs/vcs.go
@@ -2,6 +2,16 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+// Package vcs exposes functions for resolving import paths
+// and using version control systems, which can be used to
+// implement behavior similar to the standard "go get" command.
+//
+// This package is a copy of internal code in package cmd/go/internal/get,
+// modified to make the identifiers exported. It's provided here
+// for developers who want to write tools with similar semantics.
+// It needs to be manually kept in sync with upstream when changes are
+// made to cmd/go/internal/get; see https://golang.org/issues/11490.
+//
 package vcs // import "golang.org/x/tools/go/vcs"
 
 import (