diff --git a/src/main.py b/src/main.py
index 4c791bb..604c5f5 100644
--- a/src/main.py
+++ b/src/main.py
@@ -148,6 +148,20 @@ def create_calendar_slots(datetime_start: datetime, timezone: str, slot_length_m
     return events
 
 
+@app.post('/calendar_events/busy', response_model=List[CalendarEvent])
+def mark_busy_calendar_slot(
+        lower_bound: datetime = None,
+        upper_bound: datetime = None,
+        service: Resource = Depends(get_calendar_service)
+):
+    events_dict = get_calendar_events(lower_bound=lower_bound, upper_bound=upper_bound, service=service)
+    events = list(map(lambda x: CalendarEvent(**x), events_dict))
+
+    free_slots = list(filter(lambda x: x.summary == TITLE_FREE if x.summary else False, events))
+
+    return free_slots
+
+
 @app.post('/calendar_events/mark_busy', response_model=CalendarEvent)
 def mark_busy_calendar_slot(
         description: str | None = None,