mark msvc-helper as experimental
diff --git a/src/ninja.cc b/src/ninja.cc
index 089dbc1..ad56f1c 100644
--- a/src/ninja.cc
+++ b/src/ninja.cc
@@ -538,7 +538,7 @@
       Tool::RUN_AFTER_LOAD, ToolBrowse },
 #endif
 #if defined(WIN32)
-    { "msvc", "build helper for MSVC cl.exe",
+    { "msvc", "build helper for MSVC cl.exe (EXPERIMENTAL)",
       Tool::RUN_AFTER_FLAGS, ToolMSVC },
 #endif
     { "clean", "clean built files",