How to integrate Google Calendar MCP with Vercel AI SDK

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Introduction

This guide walks you through connecting Google Calendar to Vercel AI SDK using the Composio tool router. By the end, you'll have a working Google Calendar agent that can create a meeting with the marketing team, list all events scheduled for next week, delete tomorrow’s canceled event from my calendar, update the time for friday’s project sync through natural language commands.

This guide will help you understand how to give your Vercel AI SDK agent real control over a Google Calendar account through Composio's Google Calendar 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 and configure a Vercel AI SDK agent with Google Calendar integration
  • Using Composio's Tool Router to dynamically load and access Google Calendar tools
  • Creating an MCP client connection using HTTP transport
  • Building an interactive CLI chat interface with conversation history management
  • Handling tool calls and results within the Vercel AI SDK framework

What is Vercel AI SDK?

The Vercel AI SDK is a TypeScript library for building AI-powered applications. It provides tools for creating agents that can use external services and maintain conversation state.

Key features include:

  • streamText: Core function for streaming responses with real-time tool support
  • MCP Client: Built-in support for Model Context Protocol
  • Step Counting: Control multi-step tool execution
  • OpenAI Provider: Native integration with OpenAI models

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

The Google Calendar MCP server is an implementation of the Model Context Protocol that connects your AI agent and assistants like Claude, Cursor, etc directly to your Google Calendar account. It provides structured and secure access to your calendars and events, so your agent can schedule meetings, create or modify events, list upcoming appointments, and manage calendars—all on your behalf.

  • Automated event creation and scheduling: Easily instruct your agent to add new events, meetings, or reminders with specific times, attendees, and details.
  • Event listing and agenda overview: Have your agent list all upcoming, past, or filtered events on any of your calendars to keep you on top of your schedule.
  • Calendar management and customization: Direct your agent to create new calendars, update calendar details, or even insert calendars into your list for better organization.
  • Event updating and deletion: Let your agent modify existing events or remove events that are no longer needed, keeping your calendar up to date.
  • Complete calendar clearing: Ask your agent to clear all events from a primary calendar or delete secondary calendars entirely when you need a fresh start.

Supported Tools & Triggers

Tools
Triggers
Insert Calendar into ListInserts an existing calendar into the user's calendar list.
Update Calendar List EntryUpdates an existing entry on the user\'s calendar list.
Delete CalendarDeletes a secondary calendar.
Update CalendarUpdates metadata for a calendar.
Clear CalendarClears a primary calendar.
Create EventCreates an event on a google calendar, needing rfc3339 utc start/end times (end after start) and write access to the calendar.
Delete eventDeletes a specified event by `event id` from a google calendar (`calendar id`); this action is idempotent and raises a 404 error if the event is not found.
Create a calendarCreates a new, empty google calendar with the specified title (summary).
Get Event InstancesReturns instances of the specified recurring event.
List EventsReturns events on the specified calendar.
Move EventMoves an event to another calendar, i.
Watch EventsWatch for changes to events resources.
Find eventFinds events in a specified google calendar using text query, time ranges (event start/end, last modification), and event types; ensure `timemin` is not chronologically after `timemax` if both are provided.
Find free slotsFinds free/busy time slots in google calendars for specified calendars within a defined time range (defaults to the current day utc if `time min`/`time max` are omitted), enhancing busy intervals with event details; `time min` must precede `time max` if both are provided.
Query Free/Busy InformationReturns free/busy information for a set of calendars.
Get Google CalendarRetrieves a specific google calendar, identified by `calendar id`, to which the authenticated user has access.
Get current date and timeGets the current date and time, allowing for a specific timezone offset.
List ACL RulesRetrieves the list of access control rules (acls) for a specified calendar, providing the necessary 'rule id' values required for updating specific acl rules.
List Google CalendarsRetrieves calendars from the user's google calendar list, with options for pagination and filtering.
Patch CalendarPartially updates (patches) an existing google calendar, modifying only the fields provided; `summary` is mandatory and cannot be an empty string, and an empty string for `description` or `location` clears them.
Patch EventUpdates specified fields of an existing event in a google calendar using patch semantics (array fields like `attendees` are fully replaced if provided); ensure the `calendar id` and `event id` are valid and the user has write access to the calendar.
Quick Add EventParses natural language text to quickly create a basic google calendar event with its title, date, and time, suitable for simple scheduling; does not support direct attendee addition or recurring events, and `calendar id` must be valid if not 'primary'.
Remove attendee from eventRemoves an attendee from a specified event in a google calendar; the calendar and event must exist.
List SettingsReturns all user settings for the authenticated user.
Watch SettingsWatch for changes to settings resources.
Sync EventsSynchronizes google calendar events, performing a full sync if no `sync token` is provided or if a 410 gone error (due to an expired token) necessitates it, otherwise performs an incremental sync for events changed since the `sync token` was issued.
Update ACL RuleUpdates an access control rule for the specified calendar.
Update Google eventUpdates an existing event by `event id` in a google calendar; this is a full put replacement, so provide all desired fields as unspecified ones may be cleared or reset.

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 you begin, make sure you have:
  • Node.js and npm installed
  • A Composio account with API key
  • An OpenAI API key

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 required dependencies

bash
npm install @ai-sdk/openai @ai-sdk/mcp @composio/core ai dotenv

First, install the necessary packages for your project.

What you're installing:

  • @ai-sdk/openai: Vercel AI SDK's OpenAI provider
  • @ai-sdk/mcp: MCP client for Vercel AI SDK
  • @composio/core: Composio SDK for tool integration
  • ai: Core Vercel AI SDK
  • dotenv: Environment variable management

Set up environment variables

bash
OPENAI_API_KEY=your_openai_api_key_here
COMPOSIO_API_KEY=your_composio_api_key_here
COMPOSIO_USER_ID=your_user_id_here

Create a .env file in your project root.

What's needed:

  • OPENAI_API_KEY: Your OpenAI API key for GPT model access
  • COMPOSIO_API_KEY: Your Composio API key for tool access
  • COMPOSIO_USER_ID: A unique identifier for the user session

Import required modules and validate environment

typescript
import "dotenv/config";
import { openai } from "@ai-sdk/openai";
import { Composio } from "@composio/core";
import * as readline from "readline";
import { streamText, type ModelMessage, stepCountIs } from "ai";
import { experimental_createMCPClient as createMCPClient } from "@ai-sdk/mcp";

const composioAPIKey = process.env.COMPOSIO_API_KEY;
const composioUserID = process.env.COMPOSIO_USER_ID;

if (!process.env.OPENAI_API_KEY) throw new Error("OPENAI_API_KEY is not set");
if (!composioAPIKey) throw new Error("COMPOSIO_API_KEY is not set");
if (!composioUserID) throw new Error("COMPOSIO_USER_ID is not set");

const composio = new Composio({
  apiKey: composioAPIKey,
});
What's happening:
  • We're importing all necessary libraries including Vercel AI SDK's OpenAI provider and Composio
  • The dotenv/config import automatically loads environment variables
  • The MCP client import enables connection to Composio's tool server

Create Tool Router session and initialize MCP client

typescript
async function main() {
  // Create a tool router session for the user
  const { session } = await composio.create(composioUserID!, {
    toolkits: ["googlecalendar"],
  });

  const mcpUrl = session.mcp.url;
What's happening:
  • We're creating a Tool Router session that gives your agent access to Google Calendar tools
  • The create method takes the user ID and specifies which toolkits should be available
  • The returned mcp object contains the URL and authentication headers needed to connect to the MCP server
  • This session provides access to all Google Calendar-related tools through the MCP protocol

Connect to MCP server and retrieve tools

typescript
const mcpClient = await createMCPClient({
  transport: {
    type: "http",
    url: mcpUrl,
    headers: session.mcp.headers, // Authentication headers for the Composio MCP server
  },
});

const tools = await mcpClient.tools();
What's happening:
  • We're creating an MCP client that connects to our Composio Tool Router session via HTTP
  • The mcp.url provides the endpoint, and mcp.headers contains authentication credentials
  • The type: "http" is important - Composio requires HTTP transport
  • tools() retrieves all available Google Calendar tools that the agent can use

Initialize conversation and CLI interface

typescript
let messages: ModelMessage[] = [];

console.log("Chat started! Type 'exit' or 'quit' to end the conversation.\n");
console.log(
  "Ask any questions related to googlecalendar, like summarize my last 5 emails, send an email, etc... :)))\n",
);

const rl = readline.createInterface({
  input: process.stdin,
  output: process.stdout,
  prompt: "> ",
});

rl.prompt();
What's happening:
  • We initialize an empty messages array to maintain conversation history
  • A readline interface is created to accept user input from the command line
  • Instructions are displayed to guide the user on how to interact with the agent

Handle user input and stream responses with real-time tool feedback

typescript
rl.on("line", async (userInput: string) => {
  const trimmedInput = userInput.trim();

  if (["exit", "quit", "bye"].includes(trimmedInput.toLowerCase())) {
    console.log("\nGoodbye!");
    rl.close();
    process.exit(0);
  }

  if (!trimmedInput) {
    rl.prompt();
    return;
  }

  messages.push({ role: "user", content: trimmedInput });
  console.log("\nAgent is thinking...\n");

  try {
    const stream = streamText({
      model: openai("gpt-5"),
      messages,
      tools,
      toolChoice: "auto",
      stopWhen: stepCountIs(10),
      onStepFinish: (step) => {
        for (const toolCall of step.toolCalls) {
          console.log(`[Using tool: ${toolCall.toolName}]`);
          }
          if (step.toolCalls.length > 0) {
            console.log(""); // Add space after tool calls
          }
        },
      });

      for await (const chunk of stream.textStream) {
        process.stdout.write(chunk);
      }

      console.log("\n\n---\n");

      // Get final result for message history
      const response = await stream.response;
      if (response?.messages?.length) {
        messages.push(...response.messages);
      }
    } catch (error) {
      console.error("\nAn error occurred while talking to the agent:");
      console.error(error);
      console.log(
        "\nYou can try again or restart the app if it keeps happening.\n",
      );
    } finally {
      rl.prompt();
    }
  });

  rl.on("close", async () => {
    await mcpClient.close();
    console.log("\n👋 Session ended.");
    process.exit(0);
  });
}

main().catch((err) => {
  console.error("Fatal error:", err);
  process.exit(1);
});
What's happening:
  • We use streamText instead of generateText to stream responses in real-time
  • toolChoice: "auto" allows the model to decide when to use Google Calendar tools
  • stopWhen: stepCountIs(10) allows up to 10 steps for complex multi-tool operations
  • onStepFinish callback displays which tools are being used in real-time
  • We iterate through the text stream to create a typewriter effect as the agent responds
  • The complete response is added to conversation history to maintain context
  • Errors are caught and displayed with helpful retry suggestions

Complete Code

Here's the complete code to get you started with Google Calendar and Vercel AI SDK:

typescript
import "dotenv/config";
import { openai } from "@ai-sdk/openai";
import { Composio } from "@composio/core";
import * as readline from "readline";
import { streamText, type ModelMessage, stepCountIs } from "ai";
import { experimental_createMCPClient as createMCPClient } from "@ai-sdk/mcp";

const composioAPIKey = process.env.COMPOSIO_API_KEY;
const composioUserID = process.env.COMPOSIO_USER_ID;

if (!process.env.OPENAI_API_KEY) throw new Error("OPENAI_API_KEY is not set");
if (!composioAPIKey) throw new Error("COMPOSIO_API_KEY is not set");
if (!composioUserID) throw new Error("COMPOSIO_USER_ID is not set");

const composio = new Composio({
  apiKey: composioAPIKey,
});

async function main() {
  // Create a tool router session for the user
  const { session } = await composio.create(composioUserID!, {
    toolkits: ["googlecalendar"],
  });

  const mcpUrl = session.mcp.url;

  const mcpClient = await createMCPClient({
    transport: {
      type: "http",
      url: mcpUrl,
      headers: session.mcp.headers, // Authentication headers for the Composio MCP server
    },
  });

  const tools = await mcpClient.tools();

  let messages: ModelMessage[] = [];

  console.log("Chat started! Type 'exit' or 'quit' to end the conversation.\n");
  console.log(
    "Ask any questions related to googlecalendar, like summarize my last 5 emails, send an email, etc... :)))\n",
  );

  const rl = readline.createInterface({
    input: process.stdin,
    output: process.stdout,
    prompt: "> ",
  });

  rl.prompt();

  rl.on("line", async (userInput: string) => {
    const trimmedInput = userInput.trim();

    if (["exit", "quit", "bye"].includes(trimmedInput.toLowerCase())) {
      console.log("\nGoodbye!");
      rl.close();
      process.exit(0);
    }

    if (!trimmedInput) {
      rl.prompt();
      return;
    }

    messages.push({ role: "user", content: trimmedInput });
    console.log("\nAgent is thinking...\n");

    try {
      const stream = streamText({
        model: openai("gpt-5"),
        messages,
        tools,
        toolChoice: "auto",
        stopWhen: stepCountIs(10),
        onStepFinish: (step) => {
          for (const toolCall of step.toolCalls) {
            console.log(`[Using tool: ${toolCall.toolName}]`);
          }
          if (step.toolCalls.length > 0) {
            console.log(""); // Add space after tool calls
          }
        },
      });

      for await (const chunk of stream.textStream) {
        process.stdout.write(chunk);
      }

      console.log("\n\n---\n");

      // Get final result for message history
      const response = await stream.response;
      if (response?.messages?.length) {
        messages.push(...response.messages);
      }
    } catch (error) {
      console.error("\nAn error occurred while talking to the agent:");
      console.error(error);
      console.log(
        "\nYou can try again or restart the app if it keeps happening.\n",
      );
    } finally {
      rl.prompt();
    }
  });

  rl.on("close", async () => {
    await mcpClient.close();
    console.log("\n👋 Session ended.");
    process.exit(0);
  });
}

main().catch((err) => {
  console.error("Fatal error:", err);
  process.exit(1);
});

Conclusion

You've successfully built a Google Calendar agent using the Vercel AI SDK with streaming capabilities! This implementation provides a powerful foundation for building AI applications with natural language interfaces and real-time feedback.

Key features of this implementation:

  • Real-time streaming responses for a better user experience with typewriter effect
  • Live tool execution feedback showing which tools are being used as the agent works
  • Dynamic tool loading through Composio's Tool Router with secure authentication
  • Multi-step tool execution with configurable step limits (up to 10 steps)
  • Comprehensive error handling for robust agent execution
  • Conversation history maintenance for context-aware responses

You can extend this further by adding custom error handling, implementing specific business logic, or integrating additional Composio toolkits to create multi-app workflows.

How to build Google Calendar MCP Agent with another framework

OpenAI Agents SDK

OpenAI Agents SDK

Use Google Calendar MCP with OpenAI Agents SDK

Claude Agent SDK

Claude Agent SDK

Use Google Calendar MCP with Claude Agent SDK

Google ADK

Google ADK

Use Google Calendar MCP with Google ADK

LangChain

LangChain

Use Google Calendar MCP with LangChain

Mastra AI

Mastra AI

Use Google Calendar MCP with Mastra AI

LlamaIndex

LlamaIndex

Use Google Calendar MCP with LlamaIndex

CrewAI

CrewAI

Use Google Calendar MCP with CrewAI

FAQ

What are the differences in Tool Router MCP and Google Calendar MCP?

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

Can I use Tool Router MCP with Vercel AI SDK?

Yes, you can. Vercel AI SDK 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 Google Calendar tools.

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

Yes, absolutely. You can configure which Google Calendar 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 Google Calendar data and credentials are handled as safely as possible.

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