How to integrate Calendly MCP with Pydantic AI

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Introduction

This guide walks you through connecting Calendly to Pydantic AI using the Composio tool router. By the end, you'll have a working Calendly agent that can create a single-use scheduling link for my next meeting, cancel my 2pm event with a reason, mark an invitee as no-show for today's appointment, delete all invitee data for privacy compliance through natural language commands.

This guide will help you understand how to give your Pydantic AI agent real control over a Calendly account through Composio's Calendly MCP server.

Before we dive in, let's take a quick look at the key ideas and tools involved.

TL;DR

Here's what you'll learn:
  • How to set up your Composio API key and User ID
  • How to create a Composio Tool Router session for Calendly
  • How to attach an MCP Server to a Pydantic AI agent
  • How to stream responses and maintain chat history
  • How to build a simple REPL-style chat interface to test your Calendly workflows

What is Pydantic AI?

Pydantic AI is a Python framework for building AI agents with strong typing and validation. It leverages Pydantic's data validation capabilities to create robust, type-safe AI applications.

Key features include:

  • Type Safety: Built on Pydantic for automatic data validation
  • MCP Support: Native support for Model Context Protocol servers
  • Streaming: Built-in support for streaming responses
  • Async First: Designed for async/await patterns

What is the Calendly MCP server, and what's possible with it?

The Calendly MCP server is an implementation of the Model Context Protocol that connects your AI agent and assistants like Claude, Cursor, etc directly to your Calendly account. It provides structured and secure access to your scheduling workflows, so your agent can perform actions like creating personalized scheduling links, managing events, handling invitee statuses, and automating reminders on your behalf.

  • Instant scheduling link creation: Direct your agent to generate single-use or shareable scheduling links so others can book time with you instantly—no more back-and-forth emails.
  • Automated event and invitee management: Have your agent cancel events, mark invitees as no-shows, or remove no-show statuses to keep your calendar accurate and up to date.
  • Custom one-off event setup: Empower your agent to create unique, one-off meeting types for special situations, bypassing your regular availability rules.
  • Webhook subscription automation: Let the agent set up webhook subscriptions to trigger notifications or workflows in real time when events happen in your Calendly account.
  • Data privacy and compliance actions: Instruct your agent to delete invitee data or scheduled event records as needed for privacy or regulatory compliance, especially for enterprise use cases.

Supported Tools & Triggers

Tools
Cancel eventPermanently cancels an existing, active scheduled event by its `uuid`, optionally providing a `reason`, which may trigger notifications to invitees.
Create an invitee no-showMarks an invitee, identified by their existing and valid uri, as a 'no show' for a scheduled event.
Create One-Off Event TypeCreates a temporary calendly one-off event type for unique meetings outside regular availability, requiring valid host/co-host uris, a future date/range for `date setting`, and a positive `duration`.
Create scheduling linkCreate a single-use scheduling link.
Create shareCreates a customizable, one-time share link for a calendly event type, allowing specific overrides to its settings (e.
Create single use scheduling linkCreates a one-time, single-use scheduling link for an active calendly event type, expiring after one booking.
Create webhook subscriptionCreates a calendly webhook subscription to notify a specified `url` (which must be a publicly accessible https endpoint) for selected `events` within a given `organization` and `scope`.
Delete invitee dataPermanently removes all invitee data associated with the provided emails from past organization events, for data privacy compliance (requires enterprise subscription; deletion may take up to one week).
Delete invitee no showDeletes an invitee no-show record by its `uuid` to reverse an invitee's 'no-show' status; the `uuid` must refer to an existing record.
Delete scheduled event dataFor enterprise users, initiates deletion of an organization's scheduled event data between a `start time` and `end time` (inclusive, where `start time` must be <= `end time`); actual data deletion may take up to 7 days to complete.
Delete webhook subscriptionDeletes an existing webhook subscription to stop calendly sending event notifications to its registered callback url; this operation is idempotent.
Get current userRetrieves detailed information about the currently authenticated calendly user.
Get eventUse to retrieve a specific calendly scheduled event by its uuid, provided the event exists in the user's calendly account.
Get event inviteeRetrieves detailed information about a specific invitee of a scheduled event, using their unique uuids.
Get event typeRetrieves details for a specific calendly event type, identified by its uuid, which must be valid and correspond to an existing event type.
Get groupRetrieves all attributes of a specific calendly group by its uuid; the group must exist.
Get group relationshipRetrieves a specific calendly group relationship by its valid and existing uuid, providing details on user-group associations and membership.
Get invitee no showRetrieves details for a specific invitee no show record by its uuid; an invitee no show is marked when an invitee does not attend a scheduled event.
Get organization invitationRetrieves a specific calendly organization invitation using its uuid and the parent organization's uuid.
Get organization membershipRetrieves a specific calendly organization membership by its uuid, returning all its attributes.
Get routing formRetrieves a specific routing form by its uuid, providing its configuration details including questions and routing logic.
Get userRetrieves comprehensive details for an existing calendly user.
Get user availability scheduleRetrieves an existing user availability schedule by its uuid; this schedule defines the user's default hours of availability.
Get webhook subscriptionRetrieves the details of an existing webhook subscription, identified by its uuid, including its callback url, subscribed events, scope, and state.
Invite user to organizationInvites a user to the specified calendly organization by email, if they aren't already a member and lack a pending invitation to it.
List activity log entriesRetrieves a list of activity log entries for a specified calendly organization (requires an active enterprise subscription), supporting filtering, sorting, and pagination.
List event inviteesRetrieves a list of invitees for a specified calendly event uuid, with options to filter by status or email, and sort by creation time.
List eventsRetrieves a list of scheduled calendly events; requires `user`, `organization`, `group`, or `invitee email` for scope, and admin rights may be needed when filtering by `organization` or `group`.
List event type available timesFetches available time slots for a calendly event type within a specified time range; results are not paginated.
List event type hostsRetrieves a list of hosts (users) assigned to a specific, existing calendly event type, identified by its uri.
List group relationshipsRetrieves a list of group relationships defining an owner's role (e.
List groupsReturns a list of groups for a specified calendly organization uri, supporting pagination.
List organization invitationsRetrieves a list of invitations for a specific organization, identified by its uuid.
List organization membershipsRetrieves a list of organization memberships.
List outgoing communicationsRetrieves a list of outgoing sms communications for a specified organization; requires an enterprise subscription and if filtering by creation date, both `min created at` and `max created at` must be provided to form a valid range.
List routing formsRetrieves routing forms for a specified organization; routing forms are questionnaires used to direct invitees to appropriate booking pages or external urls.
List user availability schedulesRetrieves all availability schedules for the specified calendly user.
List user busy timesFetches a user's busy time intervals (internal and external calendar events) in ascending order for a period up to 7 days; keyset pagination is not supported.
List user event typesRetrieves event types for a user or organization; requires either the `user` or `organization` uri.
List webhook subscriptionsRetrieves webhook subscriptions for a calendly organization; `scope` determines if `user` or `group` uri is also required for filtering.
Remove user from organizationRemoves a user (who is not an owner) from an organization by their membership uuid, requiring administrative privileges.
Revoke a user's organization invitationRevokes a pending and revokable (not yet accepted or expired) organization invitation using its uuid and the organization's uuid, rendering the invitation link invalid.

What is the Composio tool router, and how does it fit here?

What is Tool Router?

Composio's Tool Router helps agents find the right tools for a task at runtime. You can plug in multiple toolkits (like Gmail, HubSpot, and GitHub), and the agent will identify the relevant app and action to complete multi-step workflows. This can reduce token usage and improve the reliability of tool calls. Read more here: Getting started with Tool Router

The tool router generates a secure MCP URL that your agents can access to perform actions.

How the Tool Router works

The Tool Router follows a three-phase workflow:

  1. Discovery: Searches for tools matching your task and returns relevant toolkits with their details.
  2. Authentication: Checks for active connections. If missing, creates an auth config and returns a connection URL via Auth Link.
  3. Execution: Executes the action using the authenticated connection.

Step-by-step Guide

Prerequisites

Before starting, make sure you have:
  • Python 3.9 or higher
  • A Composio account with an active API key
  • Basic familiarity with Python and async programming

Getting API Keys for OpenAI and Composio

OpenAI API Key
  • Go to the OpenAI dashboard and create an API key. You'll need credits to use the models, or you can connect to another model provider.
  • Keep the API key safe.
Composio API Key
  • Log in to the Composio dashboard.
  • Navigate to your API settings and generate a new API key.
  • Store this key securely as you'll need it for authentication.

Install dependencies

bash
pip install composio pydantic-ai python-dotenv

Install the required libraries.

What's happening:

  • composio connects your agent to external SaaS tools like Calendly
  • pydantic-ai lets you create structured AI agents with tool support
  • python-dotenv loads your environment variables securely from a .env file

Set up environment variables

bash
COMPOSIO_API_KEY=your_composio_api_key_here
USER_ID=your_user_id_here
OPENAI_API_KEY=your_openai_api_key

Create a .env file in your project root.

What's happening:

  • COMPOSIO_API_KEY authenticates your agent to Composio's API
  • USER_ID associates your session with your account for secure tool access
  • OPENAI_API_KEY to access OpenAI LLMs

Import dependencies

python
import asyncio
import os
from dotenv import load_dotenv
from composio import Composio
from pydantic_ai import Agent
from pydantic_ai.mcp import MCPServerStreamableHTTP

load_dotenv()
What's happening:
  • We load environment variables and import required modules
  • Composio manages connections to Calendly
  • MCPServerStreamableHTTP connects to the Calendly MCP server endpoint
  • Agent from Pydantic AI lets you define and run the AI assistant

Create a Tool Router Session

python
async def main():
    api_key = os.getenv("COMPOSIO_API_KEY")
    user_id = os.getenv("USER_ID")
    if not api_key or not user_id:
        raise RuntimeError("Set COMPOSIO_API_KEY and USER_ID in your environment")

    # Create a Composio Tool Router session for Calendly
    composio = Composio(api_key=api_key)
    session = composio.create(
        user_id=user_id,
        toolkits=["calendly"],
    )
    url = session.mcp.url
    if not url:
        raise ValueError("Composio session did not return an MCP URL")
What's happening:
  • We're creating a Tool Router session that gives your agent access to Calendly tools
  • The create method takes the user ID and specifies which toolkits should be available
  • The returned session.mcp.url is the MCP server URL that your agent will use

Initialize the Pydantic AI Agent

python
# Attach the MCP server to a Pydantic AI Agent
calendly_mcp = MCPServerStreamableHTTP(url, headers={"x-api-key": COMPOSIO_API_KEY})
agent = Agent(
    "openai:gpt-5",
    toolsets=[calendly_mcp],
    instructions=(
        "You are a Calendly assistant. Use Calendly tools to help users "
        "with their requests. Ask clarifying questions when needed."
    ),
)
What's happening:
  • The MCP client connects to the Calendly endpoint
  • The agent uses GPT-5 to interpret user commands and perform Calendly operations
  • The instructions field defines the agent's role and behavior

Build the chat interface

python
# Simple REPL with message history
history = []
print("Chat started! Type 'exit' or 'quit' to end.\n")
print("Try asking the agent to help you with Calendly.\n")

while True:
    user_input = input("You: ").strip()
    if user_input.lower() in {"exit", "quit", "bye"}:
        print("\nGoodbye!")
        break
    if not user_input:
        continue

    print("\nAgent is thinking...\n", flush=True)

    async with agent.run_stream(user_input, message_history=history) as stream_result:
        collected_text = ""
        async for chunk in stream_result.stream_output():
            text_piece = None
            if isinstance(chunk, str):
                text_piece = chunk
            elif hasattr(chunk, "delta") and isinstance(chunk.delta, str):
                text_piece = chunk.delta
            elif hasattr(chunk, "text"):
                text_piece = chunk.text
            if text_piece:
                collected_text += text_piece
        result = stream_result

    print(f"Agent: {collected_text}\n")
    history = result.all_messages()
What's happening:
  • The agent reads input from the terminal and streams its response
  • Calendly API calls happen automatically under the hood
  • The model keeps conversation history to maintain context across turns

Run the application

python
if __name__ == "__main__":
    asyncio.run(main())
What's happening:
  • The asyncio loop launches the agent and keeps it running until you exit

Complete Code

Here's the complete code to get you started with Calendly and Pydantic AI:

python
import asyncio
import os
from dotenv import load_dotenv
from composio import Composio
from pydantic_ai import Agent
from pydantic_ai.mcp import MCPServerStreamableHTTP

load_dotenv()

async def main():
    api_key = os.getenv("COMPOSIO_API_KEY")
    user_id = os.getenv("USER_ID")
    if not api_key or not user_id:
        raise RuntimeError("Set COMPOSIO_API_KEY and USER_ID in your environment")

    # Create a Composio Tool Router session for Calendly
    composio = Composio(api_key=api_key)
    session = composio.create(
        user_id=user_id,
        toolkits=["calendly"],
    )
    url = session.mcp.url
    if not url:
        raise ValueError("Composio session did not return an MCP URL")

    # Attach the MCP server to a Pydantic AI Agent
    calendly_mcp = MCPServerStreamableHTTP(url, headers={"x-api-key": COMPOSIO_API_KEY})
    agent = Agent(
        "openai:gpt-5",
        toolsets=[calendly_mcp],
        instructions=(
            "You are a Calendly assistant. Use Calendly tools to help users "
            "with their requests. Ask clarifying questions when needed."
        ),
    )

    # Simple REPL with message history
    history = []
    print("Chat started! Type 'exit' or 'quit' to end.\n")
    print("Try asking the agent to help you with Calendly.\n")

    while True:
        user_input = input("You: ").strip()
        if user_input.lower() in {"exit", "quit", "bye"}:
            print("\nGoodbye!")
            break
        if not user_input:
            continue

        print("\nAgent is thinking...\n", flush=True)

        async with agent.run_stream(user_input, message_history=history) as stream_result:
            collected_text = ""
            async for chunk in stream_result.stream_output():
                text_piece = None
                if isinstance(chunk, str):
                    text_piece = chunk
                elif hasattr(chunk, "delta") and isinstance(chunk.delta, str):
                    text_piece = chunk.delta
                elif hasattr(chunk, "text"):
                    text_piece = chunk.text
                if text_piece:
                    collected_text += text_piece
            result = stream_result

        print(f"Agent: {collected_text}\n")
        history = result.all_messages()

if __name__ == "__main__":
    asyncio.run(main())

Conclusion

You've built a Pydantic AI agent that can interact with Calendly through Composio's Tool Router. With this setup, your agent can perform real Calendly actions through natural language. You can extend this further by:
  • Adding other toolkits like Gmail, HubSpot, or Salesforce
  • Building a web-based chat interface around this agent
  • Using multiple MCP endpoints to enable cross-app workflows (for example, Gmail + Calendly for workflow automation)
This architecture makes your AI agent "agent-native", able to securely use APIs in a unified, composable way without custom integrations.

How to build Calendly MCP Agent with another framework

OpenAI Agents SDK

OpenAI Agents SDK

Use Calendly MCP with OpenAI Agents SDK

Claude Agent SDK

Claude Agent SDK

Use Calendly MCP with Claude Agent SDK

Google ADK

Google ADK

Use Calendly MCP with Google ADK

LangChain

LangChain

Use Calendly MCP with LangChain

Vercel AI SDK

Vercel AI SDK

Use Calendly MCP with Vercel AI SDK

Mastra AI

Mastra AI

Use Calendly MCP with Mastra AI

LlamaIndex

LlamaIndex

Use Calendly MCP with LlamaIndex

CrewAI

CrewAI

Use Calendly MCP with CrewAI

FAQ

What are the differences in Tool Router MCP and Calendly MCP?

With a standalone Calendly MCP server, the agents and LLMs can only access a fixed set of Calendly tools tied to that server. However, with the Composio Tool Router, agents can dynamically load tools from Calendly and many other apps based on the task at hand, all through a single MCP endpoint.

Can I use Tool Router MCP with Pydantic AI?

Yes, you can. Pydantic AI fully supports MCP integration. You get structured tool calling, message history handling, and model orchestration while Tool Router takes care of discovering and serving the right Calendly tools.

Can I manage the permissions and scopes for Calendly while using Tool Router?

Yes, absolutely. You can configure which Calendly scopes and actions are allowed when connecting your account to Composio. You can also bring your own OAuth credentials or API configuration so you keep full control over what the agent can do.

How safe is my data with Composio Tool Router?

All sensitive data such as tokens, keys, and configuration is fully encrypted at rest and in transit. Composio is SOC 2 Type 2 compliant and follows strict security practices so your Calendly data and credentials are handled as safely as possible.

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