discovery: update comments

   Add comments on the limitation of maximum
   number of attributes/attachments

Change-Id: I1d33bd6ad0eb3af88612ca2b790588dc4896ee73
diff --git a/discovery/discovery.vdl.go b/discovery/discovery.vdl.go
index f01f6f5..3a28bb2 100644
--- a/discovery/discovery.vdl.go
+++ b/discovery/discovery.vdl.go
@@ -253,15 +253,19 @@
 	//
 	// The key must be US-ASCII printable characters, excluding the '=' character
 	// and should not start with '_' character.
+	//
+	// We limit the maximum number of attachments to 32.
 	Attributes Attributes
 	// Attachments as a key/value pair.
 	// E.g., {'thumbnail': binary_data }.
 	//
 	// Unlike attributes, attachments are for binary data and they are not queryable.
-	// We limit the maximum size of a single attachment to 4K bytes.
 	//
 	// The key must be US-ASCII printable characters, excluding the '=' character
 	// and should not start with '_' character.
+	//
+	// We limit the maximum number of attachments to 32 and the maximum size of each
+	// attachment is 4K bytes.
 	Attachments Attachments
 }
 
diff --git a/discovery/types.vdl b/discovery/types.vdl
index a0f4962..03b37b7 100644
--- a/discovery/types.vdl
+++ b/discovery/types.vdl
@@ -28,16 +28,20 @@
 	//
 	// The key must be US-ASCII printable characters, excluding the '=' character
 	// and should not start with '_' character.
+	//
+	// We limit the maximum number of attachments to 32.
 	Attributes Attributes
 
 	// Attachments as a key/value pair.
 	// E.g., {'thumbnail': binary_data }.
 	//
 	// Unlike attributes, attachments are for binary data and they are not queryable.
-	// We limit the maximum size of a single attachment to 4K bytes.
 	//
 	// The key must be US-ASCII printable characters, excluding the '=' character
 	// and should not start with '_' character.
+	//
+	// We limit the maximum number of attachments to 32 and the maximum size of each
+	// attachment is 4K bytes.
 	Attachments Attachments
 }