diff --git a/api/server-server/definitions/event-schemas/m.direct_to_device.yaml b/api/server-server/definitions/event-schemas/m.direct_to_device.yaml
new file mode 100644
index 000000000..48cdc4ed7
--- /dev/null
+++ b/api/server-server/definitions/event-schemas/m.direct_to_device.yaml
@@ -0,0 +1,68 @@
+# Copyright 2018 New Vector Ltd
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+type: object
+title: m.direct_to_device
+description: |-
+  An EDU that lets servers push send events directly to a specific device on
+  a remote server - for instance, to maintain an Olm E2E encrypted message channel
+  between a local and remote device.
+allOf:
+  - $ref: ../edu.yaml
+  - type: object
+    properties:
+      edu_type:
+        type: enum
+        enum: ['m.direct_to_device']
+        description: The string ``m.direct_to_device``
+        example: "m.direct_to_device"
+      content:
+        type: object
+        description: The description of the direct-to-device message
+        title: To Device Message
+        properties:
+          sender:
+            type: string
+            description: user ID of the sender
+            example: "john@example.com"
+          type:
+            type: string
+            description: event type for the message
+            example: "m.room_key_request"
+          message_id:
+            type: string
+            description: unique ID for the message, used for idempotence.  Arbitrary
+              utf8 string, of maximum length 32 codepoints.
+            example: "hiezohf6Hoo7kaev"
+          messages:
+            type: object
+            description: |-
+              The contents of the messages to be sent.  These are arranged in
+              a map of user IDs to a map of device IDs to message bodies.
+              The device ID may also be *, meaning all known devices for the user.
+            example: {
+              "alice@example.org": {
+                "IWHQUZUIAH": {
+                  "algorithm": "m.megolm.v1.aes-sha2",
+                  "room_id": "!Cuyf34gef24t:localhost",
+                  "session_id": "X3lUlvLELLYxeTx4yOVu6UDpasGEVO0Jbu+QFnm0cKQ",
+                  "session_key": "AgAAAADxKHa9uFxcXzwYoNueL5Xqi69IkD4sni8LlfJL7qNBEY..."
+                }
+              }
+            }
+        required:
+          - sender
+          - type
+          - message_id
+          - messages
diff --git a/specification/server_server_api.rst b/specification/server_server_api.rst
index 36d7d5d42..9f11ce9c9 100644
--- a/specification/server_server_api.rst
+++ b/specification/server_server_api.rst
@@ -1020,19 +1020,7 @@ EDU. There are no PDUs or Federation Queries involved.
 Each send-to-device message should be sent to the destination server using
 the following EDU::
 
-  EDU type: m.direct_to_device
-
-  Content keys:
-    sender: user ID of the sender
-
-    type: event type for the message
-
-    message_id: unique id for the message: used for idempotence
-
-    messages: The messages to send. A map from user ID, to a map from device ID
-        to message body. The device ID may also be *, meaning all known devices
-        for the user
-
+{{definition_ss_event_schemas_m_direct_to_device}}
 
 Content Repository
 ------------------