diff --git a/docs/reference/data-streams/tsds.asciidoc b/docs/reference/data-streams/tsds.asciidoc
index d70f314205c65..9c3151a509b14 100644
--- a/docs/reference/data-streams/tsds.asciidoc
+++ b/docs/reference/data-streams/tsds.asciidoc
@@ -56,6 +56,8 @@ documents, the document `_id` is a hash of the document's dimensions and
 * A TSDS uses <<synthetic-source,synthetic `_source`>>, and as a result is
 subject to a number of <<synthetic-source-restrictions,restrictions>>.
 
+NOTE: A time series index can contain fields other than dimensions or metrics.
+
 [discrete]
 [[time-series]]
 === What is a time series?