diff --git a/synapse/handlers/_base.py b/synapse/handlers/_base.py
index d00685c389..6264aa0d9a 100644
--- a/synapse/handlers/_base.py
+++ b/synapse/handlers/_base.py
@@ -36,6 +36,10 @@ class BaseHandler(object):
     """
 
     def __init__(self, hs):
+        """
+        Args:
+            hs (synapse.server.HomeServer):
+        """
         self.store = hs.get_datastore()
         self.auth = hs.get_auth()
         self.notifier = hs.get_notifier()
diff --git a/synapse/handlers/auth.py b/synapse/handlers/auth.py
index ce9bc18849..8f83923ddb 100644
--- a/synapse/handlers/auth.py
+++ b/synapse/handlers/auth.py
@@ -45,6 +45,10 @@ class AuthHandler(BaseHandler):
     SESSION_EXPIRE_MS = 48 * 60 * 60 * 1000
 
     def __init__(self, hs):
+        """
+        Args:
+            hs (synapse.server.HomeServer):
+        """
         super(AuthHandler, self).__init__(hs)
         self.checkers = {
             LoginType.PASSWORD: self._check_password_auth,
diff --git a/synapse/rest/client/v1/base.py b/synapse/rest/client/v1/base.py
index 1c020b7e2c..96b49b01f2 100644
--- a/synapse/rest/client/v1/base.py
+++ b/synapse/rest/client/v1/base.py
@@ -52,6 +52,10 @@ class ClientV1RestServlet(RestServlet):
     """
 
     def __init__(self, hs):
+        """
+        Args:
+            hs (synapse.server.HomeServer):
+        """
         self.hs = hs
         self.handlers = hs.get_handlers()
         self.builder_factory = hs.get_event_builder_factory()
diff --git a/synapse/rest/client/v1/register.py b/synapse/rest/client/v1/register.py
index 8e1f1b7845..efe796c65f 100644
--- a/synapse/rest/client/v1/register.py
+++ b/synapse/rest/client/v1/register.py
@@ -52,6 +52,10 @@ class RegisterRestServlet(ClientV1RestServlet):
     PATTERNS = client_path_patterns("/register$", releases=(), include_in_unstable=False)
 
     def __init__(self, hs):
+        """
+        Args:
+            hs (synapse.server.HomeServer): server
+        """
         super(RegisterRestServlet, self).__init__(hs)
         # sessions are stored as:
         # self.sessions = {
diff --git a/synapse/rest/client/v2_alpha/register.py b/synapse/rest/client/v2_alpha/register.py
index 5db953a1e3..2722a58e3e 100644
--- a/synapse/rest/client/v2_alpha/register.py
+++ b/synapse/rest/client/v2_alpha/register.py
@@ -45,6 +45,10 @@ class RegisterRequestTokenRestServlet(RestServlet):
     PATTERNS = client_v2_patterns("/register/email/requestToken$")
 
     def __init__(self, hs):
+        """
+        Args:
+            hs (synapse.server.HomeServer): server
+        """
         super(RegisterRequestTokenRestServlet, self).__init__()
         self.hs = hs
         self.identity_handler = hs.get_handlers().identity_handler
@@ -77,7 +81,12 @@ class RegisterRestServlet(RestServlet):
     PATTERNS = client_v2_patterns("/register$")
 
     def __init__(self, hs):
+        """
+        Args:
+            hs (synapse.server.HomeServer): server
+        """
         super(RegisterRestServlet, self).__init__()
+
         self.hs = hs
         self.auth = hs.get_auth()
         self.store = hs.get_datastore()
diff --git a/synapse/server.pyi b/synapse/server.pyi
new file mode 100644
index 0000000000..902f725c06
--- /dev/null
+++ b/synapse/server.pyi
@@ -0,0 +1,21 @@
+import synapse.handlers
+import synapse.handlers.auth
+import synapse.handlers.device
+import synapse.storage
+import synapse.state
+
+class HomeServer(object):
+    def get_auth_handler(self) -> synapse.handlers.auth.AuthHandler:
+        pass
+
+    def get_datastore(self) -> synapse.storage.DataStore:
+        pass
+
+    def get_device_handler(self) -> synapse.handlers.device.DeviceHandler:
+        pass
+
+    def get_handlers(self) -> synapse.handlers.Handlers:
+        pass
+
+    def get_state_handler(self) -> synapse.state.StateHandler:
+        pass