diff --git a/oauth2client/client.py b/oauth2client/client.py
index c8d0941..0433600 100644
--- a/oauth2client/client.py
+++ b/oauth2client/client.py
@@ -37,12 +37,12 @@
 
 
 class FlowExchangeError(Error):
-  """Error occurred during request."""
+  """Error trying to exchange an authorization grant for an access token."""
   pass
 
 
 class AccessTokenRefreshError(Error):
-  """Error occurred during request."""
+  """Error trying to refresh an expired access token."""
   pass