diff --git a/server/site_tests/tast/control.graphics-igt-nightly b/server/site_tests/tast/control.graphics-igt-nightly
index 0444a97..d72f97a 100644
--- a/server/site_tests/tast/control.graphics-igt-nightly
+++ b/server/site_tests/tast/control.graphics-igt-nightly
@@ -21,6 +21,9 @@
 more information.
 
 This test runs igt-gpu-tools against a remote DUT.
+Separate control files are needed because Tast doesn't isolate tests from each
+other and a clean device state is needed by rebooting before running a
+different graphics suite.
 
 See http://go/tast-failures for information about investigating failures.
 '''
diff --git a/server/site_tests/tast/control.graphics-igt-perbuild b/server/site_tests/tast/control.graphics-igt-perbuild
index e297575..e958a9f 100644
--- a/server/site_tests/tast/control.graphics-igt-perbuild
+++ b/server/site_tests/tast/control.graphics-igt-perbuild
@@ -21,6 +21,9 @@
 more information.
 
 This test runs igt-gpu-tools against a remote DUT.
+Separate control files are needed because Tast doesn't isolate tests from each
+other and a clean device state is needed by rebooting before running a
+different graphics suite.
 
 See http://go/tast-failures for information about investigating failures.
 '''
diff --git a/server/site_tests/tast/control.graphics-igt-weekly b/server/site_tests/tast/control.graphics-igt-weekly
index 16425cb..f2073dc 100644
--- a/server/site_tests/tast/control.graphics-igt-weekly
+++ b/server/site_tests/tast/control.graphics-igt-weekly
@@ -21,6 +21,9 @@
 more information.
 
 This test runs igt-gpu-tools against a remote DUT.
+Separate control files are needed because Tast doesn't isolate tests from each
+other and a clean device state is needed by rebooting before running a
+different graphics suite.
 
 See http://go/tast-failures for information about investigating failures.
 '''