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 3504e81..a407856 100644
--- a/Documentation/cmd-review.txt
+++ b/Documentation/cmd-review.txt
@@ -129,8 +129,8 @@
 -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.
+	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.
 
diff --git a/Documentation/rest-api-changes.txt b/Documentation/rest-api-changes.txt
index bb87056..02f14aa 100644
--- a/Documentation/rest-api-changes.txt
+++ b/Documentation/rest-api-changes.txt
@@ -5544,7 +5544,8 @@
 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.
+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`|
@@ -5800,7 +5801,8 @@
 |`message`            ||The text left by the user.
 |`tag`                 |optional|
 Value of the `tag` field from link:#review-input[ReviewInput] set
-while posting the review.
+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|
@@ -5921,7 +5923,8 @@
 |`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`
@@ -6689,8 +6692,8 @@
 |`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.