Document "autogenerated:" prefix for REST robot comments

Bug: Issue 6357
Change-Id: I00f0c53b73293d33135e14cd2878624fb877085f
diff --git a/Documentation/cmd-review.txt b/Documentation/cmd-review.txt
index 59ed6ff..998b143 100644
--- a/Documentation/cmd-review.txt
+++ b/Documentation/cmd-review.txt
@@ -129,9 +129,9 @@
 -t::
   Apply a 'TAG' to the change message, votes, and inline comments. The 'TAG'
   can represent an external system like CI that does automated verification
-  of the change. Comments with specific 'TAG' values can be filtered out in
-  the web UI.
-  Note that to apply different tags on on different votes/comments, multiple
+  of the change. Comments that contain TAG values with 'autogenerated:' prefix
+  can be filtered out in the web UI.
+  Note that to apply different tags on different votes/comments, multiple
   invocations of the SSH command are required.
 
 == ACCESS
diff --git a/Documentation/rest-api-changes.txt b/Documentation/rest-api-changes.txt
index b824bce..a565bbe 100644
--- a/Documentation/rest-api-changes.txt
+++ b/Documentation/rest-api-changes.txt
@@ -5589,8 +5589,9 @@
 The time and date describing when the approval was made.
 |`tag`                    |optional|
 Value of the `tag` field from link:#review-input[ReviewInput] set
-while posting the review.
-NOTE: To apply different tags on on different votes/comments multiple
+while posting the review. Votes/comments that contain `tag` with
+'autogenerated:' prefix can be filtered out in the web UI.
+NOTE: To apply different tags on different votes/comments multiple
 invocations of the REST call are required.
 |`post_submit` |not set if `false`|
 If true, this vote was made after the change was submitted.
@@ -5853,8 +5854,9 @@
 |`message`            ||The text left by the user.
 |`tag`                 |optional|
 Value of the `tag` field from link:#review-input[ReviewInput] set
-while posting the review.
-NOTE: To apply different tags on on different votes/comments multiple
+while posting the review. Votes/comments that contain `tag` with
+'autogenerated:' prefix can be filtered out in the web UI.
+NOTE: To apply different tags on different votes/comments multiple
 invocations of the REST call are required.
 |`_revision_number`    |optional|
 Which patchset (if any) generated this message.
@@ -5974,7 +5976,8 @@
 |`tag`         |optional, drafts only|
 Value of the `tag` field. Only allowed on link:#create-draft[draft comment] +
 inputs; for published comments, use the `tag` field in +
-link#review-input[ReviewInput]
+link#review-input[ReviewInput]. Votes/comments that contain `tag` with
+'autogenerated:' prefix can be filtered out in the web UI.
 |`unresolved`        |optional|
 Whether or not the comment must be addressed by the user. This value will
 default to false if the comment is an orphan, or the value of the `in_reply_to`
@@ -6792,8 +6795,8 @@
 |`tag`                    |optional|
 Apply this tag to the review comment message, votes, and inline
 comments. Tags may be used by CI or other automated systems to
-distinguish them from human reviews. Comments with specific tag
-values can be filtered out in the web UI.
+distinguish them from human reviews. Votes/comments that contain `tag` with
+'autogenerated:' prefix can be filtered out in the web UI.
 |`labels`                 |optional|
 The votes that should be added to the revision as a map that maps the
 label names to the voting values.