diff --git a/api/server-server/definitions/send_join_response.yaml b/api/server-server/definitions/send_join_response.yaml
index 96ceaefc..2837556b 100644
--- a/api/server-server/definitions/send_join_response.yaml
+++ b/api/server-server/definitions/send_join_response.yaml
@@ -22,9 +22,10 @@ properties:
   auth_chain:
     type: array
     description: |-
-      The auth chain. Note that events have a different format depending on
-      the room version - check the `room version specification`_ for precise
-      event formats.
+      The auth chain for the entire current room state prior to the join event.
+
+      Note that events have a different format depending on the room version - check the
+      `room version specification`_ for precise event formats.
     items:
       type: object
       title: PDU
@@ -39,8 +40,10 @@ properties:
   state:
     type: array
     description: |-
-      The room state. The event format varies depending on the room version -
-      check the `room version specification`_ for precise event formats.
+      The resolved current room state prior to the join event.
+
+      The event format varies depending on the room version - check the `room version specification`_
+      for precise event formats.
     items:
       type: object
       title: PDU
diff --git a/changelogs/server_server/newsfragments/2575.clarification b/changelogs/server_server/newsfragments/2575.clarification
new file mode 100644
index 00000000..5eb18394
--- /dev/null
+++ b/changelogs/server_server/newsfragments/2575.clarification
@@ -0,0 +1 @@
+Clarify the state/auth chain requirements for ``/send_join``.