diff --git a/nextcloud_mcp_server/models/deck.py b/nextcloud_mcp_server/models/deck.py
index ca46562..8c42bff 100644
--- a/nextcloud_mcp_server/models/deck.py
+++ b/nextcloud_mcp_server/models/deck.py
@@ -264,14 +264,14 @@ class CreateLabelResponse(BaseResponse):
 class ListCardsResponse(BaseResponse):
     """Response model for listing deck cards."""
 
-    cards: List[DeckCard] = Field(description="List of deck cards")
+    cards: list[DeckCard] = Field(description="List of deck cards")
     total: int = Field(description="Total number of cards")
 
 
 class ListLabelsResponse(BaseResponse):
     """Response model for listing deck labels."""
 
-    labels: List[DeckLabel] = Field(description="List of deck labels")
+    labels: list[DeckLabel] = Field(description="List of deck labels")
     total: int = Field(description="Total number of labels")
 
 
diff --git a/nextcloud_mcp_server/server/calendar.py b/nextcloud_mcp_server/server/calendar.py
index 0761a72..8881186 100644
--- a/nextcloud_mcp_server/server/calendar.py
+++ b/nextcloud_mcp_server/server/calendar.py
@@ -44,7 +44,8 @@ def _event_dict_to_summary(event: dict) -> CalendarEventSummary:
         categories=categories,
         status=event.get("status"),
         calendar_name=event.get("calendar_name"),
-        calendar_display_name=event.get("calendar_display_name"),
+        calendar_display_name=event.get("calendar_display_name")
+        or event.get("calendar_name"),
     )
 
 
diff --git a/nextcloud_mcp_server/server/contacts.py b/nextcloud_mcp_server/server/contacts.py
index ca64af7..7618988 100644
--- a/nextcloud_mcp_server/server/contacts.py
+++ b/nextcloud_mcp_server/server/contacts.py
@@ -66,6 +66,8 @@ def configure_contacts_tools(mcp: FastMCP):
         addressbooks_data = await client.contacts.list_addressbooks()
         addressbooks = [
             AddressBook(
+                # ab["name"] is a short slug like "contacts", not a full CardDAV URI;
+                # all tools use it as a path segment: f"{carddav_path}/{name}/"
                 uri=ab["name"],
                 displayname=ab.get("display_name", ab["name"]),
                 ctag=ab.get("getctag"),
diff --git a/tests/unit/test_response_models.py b/tests/unit/test_response_models.py
index 10cec40..56c781e 100644
--- a/tests/unit/test_response_models.py
+++ b/tests/unit/test_response_models.py
@@ -477,7 +477,7 @@ def test_event_dict_to_summary_missing_optional_fields():
 
 @pytest.mark.unit
 def test_event_dict_to_summary_calendar_name_without_display_name():
-    """Test single-calendar path: calendar_name set, display_name absent."""
+    """Test single-calendar path: calendar_name set, display_name absent falls back."""
     event = {
         "uid": "evt-006",
         "title": "Personal Errand",
@@ -487,4 +487,4 @@ def test_event_dict_to_summary_calendar_name_without_display_name():
     summary = _event_dict_to_summary(event)
 
     assert summary.calendar_name == "personal"
-    assert summary.calendar_display_name is None
+    assert summary.calendar_display_name == "personal"