diff --git a/cmd/oracle/main.go b/cmd/oracle/main.go
index 42b18d08..cbdc3dd0 100644
--- a/cmd/oracle/main.go
+++ b/cmd/oracle/main.go
@@ -6,6 +6,10 @@
 // http://golang.org/s/oracle-design
 // http://golang.org/s/oracle-user-manual
 //
+// DEPRECATED: oracle has been superseded by guru;
+// see https://golang.org/s/using-guru for details.
+// This package will be deleted on October 1, 2016.
+//
 // Run with -help flag or help subcommand for usage information.
 //
 package main // import "golang.org/x/tools/cmd/oracle"
diff --git a/oracle/oracle.go b/oracle/oracle.go
index 794cbe90..c84ebd35 100644
--- a/oracle/oracle.go
+++ b/oracle/oracle.go
@@ -7,8 +7,9 @@
 // Package oracle contains the implementation of the oracle tool whose
 // command-line is provided by golang.org/x/tools/cmd/oracle.
 //
-// http://golang.org/s/oracle-design
-// http://golang.org/s/oracle-user-manual
+// DEPRECATED: oracle has been superseded by guru;
+// see https://golang.org/s/using-guru for details.
+// This package will be deleted on October 1, 2016.
 //
 package oracle // import "golang.org/x/tools/oracle"