diff --git a/artiq/master/worker.py b/artiq/master/worker.py
index e6b42724f..7d732bfe9 100644
--- a/artiq/master/worker.py
+++ b/artiq/master/worker.py
@@ -160,8 +160,7 @@ class Worker:
                 return True
             elif action == "pause":
                 return False
-            del obj["action"]
-            if action == "create_watchdog":
+            elif action == "create_watchdog":
                 func = self.create_watchdog
             elif action == "delete_watchdog":
                 func = self.delete_watchdog
@@ -172,7 +171,7 @@ class Worker:
             if getattr(func, "worker_pass_rid", False):
                 func = partial(func, self.rid)
             try:
-                data = func(**obj)
+                data = func(*obj["args"], **obj["kwargs"])
                 reply = {"status": "ok", "data": data}
             except:
                 reply = {"status": "failed",
diff --git a/artiq/master/worker_impl.py b/artiq/master/worker_impl.py
index 40189e374..722fcb75c 100644
--- a/artiq/master/worker_impl.py
+++ b/artiq/master/worker_impl.py
@@ -26,12 +26,9 @@ class ParentActionError(Exception):
     pass
 
 
-def make_parent_action(action, argnames, exception=ParentActionError):
-    argnames = argnames.split()
-    def parent_action(*args):
-        request = {"action": action}
-        for argname, arg in zip(argnames, args):
-            request[argname] = arg
+def make_parent_action(action, exception=ParentActionError):
+    def parent_action(*args, **kwargs):
+        request = {"action": action, "args": args, "kwargs": kwargs}
         put_object(request)
         reply = get_object()
         if "action" in reply:
@@ -50,7 +47,7 @@ class LogForwarder:
     def __init__(self):
         self.buffer = ""
 
-    to_parent = staticmethod(make_parent_action("log", "message"))
+    to_parent = staticmethod(make_parent_action("log"))
 
     def write(self, data):
         self.buffer += data
@@ -64,18 +61,18 @@ class LogForwarder:
 
 
 class ParentDeviceDB:
-    get_device_db = make_parent_action("get_device_db", "")
-    get = make_parent_action("get_device", "key", KeyError)
+    get_device_db = make_parent_action("get_device_db")
+    get = make_parent_action("get_device", KeyError)
 
 
 class ParentDatasetDB:
-    get = make_parent_action("get_dataset", "key", KeyError)
-    update = make_parent_action("update_dataset", "mod")
+    get = make_parent_action("get_dataset", KeyError)
+    update = make_parent_action("update_dataset")
 
 
 class Watchdog:
-    _create = make_parent_action("create_watchdog", "t")
-    _delete = make_parent_action("delete_watchdog", "wid")
+    _create = make_parent_action("create_watchdog")
+    _delete = make_parent_action("delete_watchdog")
 
     def __init__(self, t):
         self.t = t
@@ -91,15 +88,14 @@ set_watchdog_factory(Watchdog)
 
 
 class Scheduler:
-    pause_noexc = staticmethod(make_parent_action("pause", ""))
+    pause_noexc = staticmethod(make_parent_action("pause"))
 
     def pause(self):
         if self.pause_noexc():
             raise TerminationRequested
 
-    submit = staticmethod(make_parent_action("scheduler_submit",
-        "pipeline_name expid priority due_date flush"))
-    cancel = staticmethod(make_parent_action("scheduler_cancel", "rid"))
+    submit = staticmethod(make_parent_action("scheduler_submit"))
+    cancel = staticmethod(make_parent_action("scheduler_cancel"))
 
     def set_run_info(self, pipeline_name, expid, priority):
         self.pipeline_name = pipeline_name
@@ -120,22 +116,21 @@ def get_exp(file, class_name):
         return getattr(module, class_name)
 
 
-register_experiment = make_parent_action("register_experiment",
-                                         "class_name name arguments")
+register_experiment = make_parent_action("register_experiment")
 
 
 class ExamineDeviceMgr:
-    get_device_db = make_parent_action("get_device_db", "")
+    get_device_db = make_parent_action("get_device_db")
 
-    def get(self, name):
+    def get(name):
         return None
 
 
 class DummyDatasetMgr:
-    def set(self, key, value, broadcast=False, persist=False, save=True):
+    def set(key, value, broadcast=False, persist=False, save=True):
         return None
 
-    def get(self, key):
+    def get(key):
         pass
 
 
@@ -213,7 +208,7 @@ def main():
                     f.close()
                 put_object({"action": "completed"})
             elif action == "examine":
-                examine(ExamineDeviceMgr(), DummyDatasetMgr(), obj["file"])
+                examine(ExamineDeviceMgr, DummyDatasetMgr, obj["file"])
                 put_object({"action": "completed"})
             elif action == "terminate":
                 break