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Generative AI > Google Gemini API > ADK with Google Calendar - Scheduling and Events

ADK with Google Calendar - Scheduling and Events

Author: Venkata Sudhakar

A Google Calendar-connected ADK agent can schedule meetings, check staff availability, and send invites - all triggered by natural language. ShopMax India uses this to let store managers book vendor meetings and schedule delivery slots without leaving their chat interface.

The Calendar API requires the calendar scope. Using a service account with domain-wide delegation, the agent can act on behalf of any user in the Google Workspace organisation. The agent reads free/busy slots and creates events with attendees, location, and descriptions automatically.

The below example shows an ADK agent that checks availability and creates a calendar event.

from google.adk.agents import LlmAgent
from google.adk.tools import FunctionTool
from google.adk.sessions import InMemorySessionService
from google.adk.runners import Runner
from google.oauth2 import service_account
from googleapiclient.discovery import build
from datetime import datetime, timedelta
import pytz

SCOPES = ["https://www.googleapis.com/auth/calendar"]
IST = pytz.timezone("Asia/Kolkata")

def get_cal_service(user_email: str):
    creds = service_account.Credentials.from_service_account_file(
        "/secrets/sa-key.json", scopes=SCOPES
    ).with_subject(user_email)
    return build("calendar", "v3", credentials=creds)

def check_availability(user_email: str, date_str: str) -> dict:
    """Check free slots for a user on a given date (YYYY-MM-DD)."""
    svc = get_cal_service(user_email)
    day = datetime.strptime(date_str, "%Y-%m-%d").replace(tzinfo=IST)
    time_min = day.replace(hour=9, minute=0).isoformat()
    time_max = day.replace(hour=18, minute=0).isoformat()
    body = {"timeMin": time_min, "timeMax": time_max,
            "items": [{"id": user_email}]}
    fb = svc.freebusy().query(body=body).execute()
    busy = fb["calendars"][user_email]["busy"]
    return {"user": user_email, "date": date_str, "busy_slots": busy}

def create_event(organiser: str, title: str, date_str: str,
                 start_hour: int, duration_minutes: int,
                 attendees: list, description: str) -> dict:
    """Create a calendar event and invite attendees."""
    svc = get_cal_service(organiser)
    day = datetime.strptime(date_str, "%Y-%m-%d").replace(tzinfo=IST)
    start = day.replace(hour=start_hour, minute=0)
    end = start + timedelta(minutes=duration_minutes)
    event = {
        "summary": title,
        "description": description,
        "start": {"dateTime": start.isoformat(), "timeZone": "Asia/Kolkata"},
        "end": {"dateTime": end.isoformat(), "timeZone": "Asia/Kolkata"},
        "attendees": [{"email": a} for a in attendees],
        "reminders": {"useDefault": True},
    }
    created = svc.events().insert(calendarId="primary", body=event,
                                  sendUpdates="all").execute()
    return {"status": "created", "event_id": created["id"], "link": created.get("htmlLink")}

agent = LlmAgent(
    name="shopmax_calendar_agent",
    model="gemini-2.0-flash",
    instruction=(
        "You are a ShopMax scheduling assistant. "
        "Check availability and create calendar events when asked. "
        "Always use IST timezone. Keep meeting durations sensible."
    ),
    tools=[FunctionTool(check_availability), FunctionTool(create_event)],
)

session_service = InMemorySessionService()
runner = Runner(agent=agent, session_service=session_service)
events = list(runner.run(
    user_id="manager1", session_id="sess_cal_001",
    new_message={"role": "user", "parts": [{
        "text": "Book a 1-hour vendor review with supplier@samsung.in and logistics@delhivery.com on 2026-04-10 at 11 AM for manager@shopmax.in"
    }]},
))
print(next(e.content.parts[0].text for e in events if e.is_final_response()))

It gives the following output,

Checking availability for [email protected] on 2026-04-10...
  Busy: 09:00-10:00, 14:00-15:30
  11:00 AM slot is free.

Event created:
  Title:     Vendor Review - Samsung & Delhivery
  Date:      10 Apr 2026, 11:00 AM - 12:00 PM IST
  Attendees: [email protected], [email protected], [email protected]
  Invites sent to all attendees.

For recurring vendor reviews, use the recurrence field in the event body with RRULE syntax. Combine the Calendar agent with the Gmail agent to automatically send a pre-meeting agenda email one hour before the event. Use Google Meet conferenceData to auto-generate a video link when attendees are in different cities like Mumbai, Bangalore, and Delhi.

Send your comments, suggestions or queries regarding this site to [email protected].