diff --git a/changelogs/client_server/newsfragments/1531.feature b/changelogs/client_server/newsfragments/1531.feature
new file mode 100644
index 00000000..a59c2177
--- /dev/null
+++ b/changelogs/client_server/newsfragments/1531.feature
@@ -0,0 +1 @@
+Add `m.annotation` relations (reactions), as per [MSC2677](https://github.com/matrix-org/matrix-spec-proposals/pull/2677).
diff --git a/content/client-server-api/modules/event_annotations.md b/content/client-server-api/modules/event_annotations.md
index 8aeff40f..661d8001 100644
--- a/content/client-server-api/modules/event_annotations.md
+++ b/content/client-server-api/modules/event_annotations.md
@@ -71,6 +71,12 @@ change their reaction, the original reaction should be redacted and a new one
 sent in its place.
 {{% /boxes/note %}}
 
+{{% boxes/note %}}
+The `key` field in `m.reaction` can be any string so clients must take care to
+render long reactions in a sensible manner. For example, clients can elide
+overly-long reactions.
+{{% /boxes/note %}}
+
 #### Server behaviour
 
 ##### Avoiding duplicate annotations
diff --git a/content/client-server-api/modules/push.md b/content/client-server-api/modules/push.md
index ad2c544b..d1855f58 100644
--- a/content/client-server-api/modules/push.md
+++ b/content/client-server-api/modules/push.md
@@ -700,7 +700,7 @@ Definition:
 
 {{% added-in v="1.7" %}}
 
-Matches any event whose type is `m.room.reaction`. This suppresses notifications for [`m.reaction`](#mreaction) events.
+Matches any event whose type is `m.reaction`. This suppresses notifications for [`m.reaction`](#mreaction) events.
 
 Definition:
 
diff --git a/content/client-server-api/modules/receipts.md b/content/client-server-api/modules/receipts.md
index 1b1af61a..8cd4e9f6 100644
--- a/content/client-server-api/modules/receipts.md
+++ b/content/client-server-api/modules/receipts.md
@@ -153,12 +153,6 @@ relationships and solid lines showing topological ordering.
 
 ![threaded-dag](/diagrams/threaded-dag.png)
 
-{{% boxes/note %}}
-`m.reaction` relationships are not currently specified, but are shown here for
-their conceptual place in a threaded DAG. They are currently proposed as
-[MSC2677](https://github.com/matrix-org/matrix-spec-proposals/pull/2677).
-{{% /boxes/note %}}
-
 This DAG can be represented as 3 threaded timelines, with `A` and `B` being thread
 roots:
 
diff --git a/data/event-schemas/schema/m.reaction.yaml b/data/event-schemas/schema/m.reaction.yaml
index 4d8ce43b..6d369c5f 100644
--- a/data/event-schemas/schema/m.reaction.yaml
+++ b/data/event-schemas/schema/m.reaction.yaml
@@ -30,8 +30,10 @@ properties:
           key:
             type: string
             description: |-
-              An emoji representing the reaction being made. Should include the
-              unicode emoji presentation selector (`\uFE0F`) for codepoints
-              which allow it (see the [emoji variation sequences
+              The reaction being made, usually an emoji.
+
+              If this is an emoji, it should include the unicode emoji
+              presentation selector (`\uFE0F`) for codepoints which allow it
+              (see the [emoji variation sequences
               list](https://www.unicode.org/Public/UCD/latest/ucd/emoji/emoji-variation-sequences.txt)).
             example: "👍"