diff --git a/changelog.d/6775.doc b/changelog.d/6775.doc
new file mode 100644
index 000000000..c6078ef82
--- /dev/null
+++ b/changelog.d/6775.doc
@@ -0,0 +1 @@
+Clarify documentation related to `user_dir` and `federation_reader` workers.
diff --git a/docs/workers.md b/docs/workers.md
index 0ab269fd9..09a9d8a7b 100644
--- a/docs/workers.md
+++ b/docs/workers.md
@@ -185,6 +185,19 @@ reverse-proxy configuration.
 The `^/_matrix/federation/v1/send/` endpoint must only be handled by a single
 instance.
 
+Note that `federation` must be added to the listener resources in the worker config:
+
+```yaml
+worker_app: synapse.app.federation_reader
+...
+worker_listeners:
+ - type: http
+   port: <port>
+   resources:
+     - names:
+       - federation
+```
+
 ### `synapse.app.federation_sender`
 
 Handles sending federation traffic to other servers. Doesn't handle any
@@ -265,6 +278,10 @@ the following regular expressions:
 
     ^/_matrix/client/(api/v1|r0|unstable)/user_directory/search$
 
+When using this worker you must also set `update_user_directory: False` in the 
+shared configuration file to stop the main synapse running background 
+jobs related to updating the user directory.
+
 ### `synapse.app.frontend_proxy`
 
 Proxies some frequently-requested client endpoints to add caching and remove