diff --git a/plugins/homeassistant/mcp_tools.py b/plugins/homeassistant/mcp_tools.py
index 544fb3b..ffdaaae 100644
--- a/plugins/homeassistant/mcp_tools.py
+++ b/plugins/homeassistant/mcp_tools.py
@@ -108,4 +108,4 @@ async def mcp_overview(db) -> list[dict]:
 
 def register_tools(register) -> None:
     register(get_home_assistant, role=UserRole.viewer, read_only=True)
-    register(update_home_assistant, role=UserRole.admin)
+    register(update_home_assistant, role=UserRole.admin, read_only=False)
diff --git a/tests/plugins/homeassistant/test_service.py b/tests/plugins/homeassistant/test_service.py
index 444c4cb..936d928 100644
--- a/tests/plugins/homeassistant/test_service.py
+++ b/tests/plugins/homeassistant/test_service.py
@@ -129,7 +129,10 @@ def test_the_overview_names_what_needs_a_look_and_no_more():
 
 def test_reading_is_open_to_a_viewer_and_installing_is_for_an_admin():
     seen = {}
-    homeassistant_plugin.register_mcp_tools(lambda fn, role, read_only=False: seen.update({fn.__name__: (role, read_only)}))
+
+    def register(fn, *, role, read_only):     # both required, as on the server
+        seen[fn.__name__] = (role, read_only)
+    homeassistant_plugin.register_mcp_tools(register)
     assert seen == {"get_home_assistant": (UserRole.viewer, True), "update_home_assistant": (UserRole.admin, False)}