How to integrate Gmail MCP with Mastra AI

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Introduction

This guide walks you through connecting Gmail to Mastra AI using the Composio tool router. By the end, you'll have a working Gmail agent that can read emails, search your inbox, draft messages, manage labels, and organize threads through natural language commands.

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

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

Also integrate Gmail with

TL;DR

Here's what you'll learn:
  • Set up your environment so Mastra, OpenAI, and Composio work together
  • Create a Tool Router session in Composio that exposes Gmail tools
  • Connect Mastra's MCP client to the Composio generated MCP URL
  • Fetch Gmail tool definitions and attach them as a toolset
  • Build a Mastra agent that can reason, call tools, and return structured results
  • Run an interactive CLI where you can chat with your Gmail agent

What is Mastra AI?

Mastra AI is a TypeScript framework for building AI agents with tool support. It provides a clean API for creating agents that can use external services through MCP.

Key features include:

  • MCP Client: Built-in support for Model Context Protocol servers
  • Toolsets: Organize tools into logical groups
  • Step Callbacks: Monitor and debug agent execution
  • OpenAI Integration: Works with OpenAI models via @ai-sdk/openai

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

The Gmail MCP server is an implementation of the Model Context Protocol that connects your AI agent and assistants like Claude, Cursor, etc directly to your Gmail account. It provides structured and secure access to your email, so your agent can search, read, draft, organize, and even manage contacts in your mailbox—all on your behalf.

  • Advanced email search and retrieval: Effortlessly instruct your agent to fetch emails by sender, subject, label, date, or keywords, and even retrieve full message content or threads.
  • Automated drafting and sending: Have your agent create new email drafts, craft replies, add CC/BCC, include attachments, and handle threading to streamline communication.
  • Smart label and inbox organization: Let the agent create new labels, apply or remove labels from emails, and keep your inbox clutter-free by archiving or moving messages.
  • Contact and thread management: Fetch your Gmail contacts, pull entire conversation threads, or download specific attachments to make follow-ups a breeze.
  • Email and draft cleanup: Direct your agent to permanently delete emails or drafts, helping you maintain a tidy mailbox with minimal effort.

Supported Tools & Triggers

Tools
Triggers
Modify email labelsAdds and/or removes specified Gmail labels for a message; ensure `message_id` and all `label_ids` are valid (use 'listLabels' for custom label IDs).
Batch delete Gmail messagesTool to permanently delete multiple Gmail messages in bulk, bypassing Trash with no recovery possible.
Batch modify Gmail messagesModify labels on multiple Gmail messages in one efficient API call.
Create email draftCreates a Gmail email draft.
Create Gmail filterTool to create a new Gmail filter with specified criteria and actions.
Create labelCreates a new label with a unique name in the specified user's Gmail account.
Create Prompt PostSend a one-shot prompt to the Sanity Content Agent.
Delete DraftPermanently deletes a specific Gmail draft using its ID with no recovery possible; verify the correct `draft_id` and obtain explicit user confirmation before calling.
Delete Gmail filterTool to permanently delete a Gmail filter by its ID.
Delete label from account (permanent)Permanently DELETES a user-created Gmail label from the account (not from a message).
Delete messagePermanently deletes a specific email message by its ID from a Gmail mailbox; for `user_id`, use 'me' for the authenticated user or an email address to which the authenticated user has delegated access.
Delete threadTool to immediately and permanently delete a specified thread and all its messages.
Fetch emailsFetches a list of email messages from a Gmail account, supporting filtering, pagination, and optional full content retrieval.
Fetch message by message IDFetches a specific email message by its ID, provided the `message_id` exists and is accessible to the authenticated `user_id`.
Fetch Message by Thread IDRetrieves messages from a Gmail thread using its `thread_id`, where the thread must be accessible by the specified `user_id`.
Forward email messageForward an existing Gmail message to specified recipients, preserving original body and attachments.
Get Gmail attachmentRetrieves a specific attachment by ID from a message in a user's Gmail mailbox, requiring valid message and attachment IDs.
Get Auto-Forwarding SettingsTool to get the auto-forwarding setting for the specified account.
Get contactsFetches contacts (connections) for the authenticated Google account, allowing selection of specific data fields and pagination.
Get DraftRetrieves a single Gmail draft by its ID.
Get Gmail filterTool to retrieve a specific Gmail filter by its ID.
Get label detailsGets details for a specified Gmail label.
Get Language SettingsTool to retrieve the language settings for a Gmail user.
Get PeopleRetrieves either a specific person's details (using `resource_name`) or lists 'Other Contacts' (if `other_contacts` is true), with `person_fields` specifying the data to return.
Get ProfileRetrieves Gmail profile information (email address, aggregate messagesTotal/threadsTotal, historyId) for a user.
Get Vacation SettingsTool to retrieve vacation responder settings for a Gmail user.
Import messageTool to import a message into the user's mailbox with standard email delivery scanning and classification.
Insert message into mailboxTool to insert a message into the user's mailbox similar to IMAP APPEND.
List CSE identitiesTool to list client-side encrypted identities for an authenticated user.
List CSE key pairsTool to list client-side encryption key pairs for an authenticated user.
List DraftsRetrieves a paginated list of email drafts from a user's Gmail account.
List Gmail filtersTool to list all Gmail filters (rules) in the mailbox.
List forwarding addressesTool to list all forwarding addresses for the specified Gmail account.
List Gmail historyTool to list Gmail mailbox change history since a known startHistoryId.
List Gmail labelsRetrieves all system and user-created labels for a Gmail account in a single unpaginated response.
List send-as aliasesLists the send-as aliases for a Gmail account, including the primary address and custom 'from' aliases.
List S/MIME configsLists S/MIME configs for the specified send-as alias.
List threadsRetrieves a list of email threads from a Gmail account, identified by `user_id` (email address or 'me'), supporting filtering and pagination.
Modify thread labelsAdds or removes specified existing label IDs from a Gmail thread, affecting all its messages; ensure the thread ID is valid.
Trash threadMoves the specified thread to the trash.
Move to TrashMoves an existing, non-deleted email message to the trash for the specified user.
Patch LabelPatches the specified user-created label.
Patch send-as aliasTool to patch the specified send-as alias for a Gmail user.
Reply to email threadSends a reply within a specific Gmail thread using the original thread's subject; do not provide a custom subject as it will start a new conversation instead of replying in-thread.
Search PeopleSearches contacts by matching the query against names, nicknames, emails, phone numbers, and organizations, optionally including 'Other Contacts'.
Send DraftSends an existing draft email AS-IS to recipients already defined within the draft.
Send EmailSends an email via Gmail API using the authenticated user's Google profile display name.
Get IMAP SettingsRetrieves the IMAP settings for a Gmail user account, including whether IMAP is enabled, auto-expunge behavior, expunge behavior, and maximum folder size.
Get POP settingsTool to retrieve POP settings for a Gmail account.
Get send-as aliasTool to retrieve a specific send-as alias configuration for a Gmail user.
Stop watch notificationsTool to stop receiving push notifications for a Gmail mailbox.
Untrash MessageTool to remove a message from trash in Gmail.
Untrash threadTool to remove a thread from trash in Gmail.
Update draftUpdates (replaces) an existing Gmail draft's content in-place by draft ID.
Update IMAP settingsTool to update IMAP settings for a Gmail account.
Update LabelTool to update the properties of an existing Gmail label.
Update Language SettingsTool to update the language settings for a Gmail user.
Update POP settingsTool to update POP settings for a Gmail account.
Update send-as aliasTool to update a send-as alias for a Gmail user.
Update User Attributes ValuesUpdate user attribute values for a resource.
Update Vacation SettingsTool to update vacation responder settings for a Gmail user.

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

What is Composio SDK?

Composio's Composio SDK 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 Composio SDK

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

How the Composio SDK works

The Composio SDK 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:
  • Node.js 18 or higher
  • A Composio account with an active API key
  • An OpenAI API key
  • Basic familiarity with TypeScript

Getting API Keys for OpenAI and Composio

OpenAI API Key
  • Go to the OpenAI dashboard and create an API key.
  • You need credits or a connected billing setup to use the models.
  • Store the key somewhere safe.
Composio API Key
  • Log in to the Composio dashboard.
  • Go to Settings and copy your API key.
  • This key lets your Mastra agent talk to Composio and reach Gmail through MCP.

Install dependencies

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

Install the required packages.

What's happening:

  • @composio/core is the Composio SDK for creating MCP sessions
  • @mastra/core provides the Agent class
  • @mastra/mcp is Mastra's MCP client
  • @ai-sdk/openai is the model wrapper for OpenAI
  • dotenv loads environment variables from .env

Set up environment variables

bash
COMPOSIO_API_KEY=your_composio_api_key_here
COMPOSIO_USER_ID=your_user_id_here
OPENAI_API_KEY=your_openai_api_key_here

Create a .env file in your project root.

What's happening:

  • COMPOSIO_API_KEY authenticates your requests to Composio
  • COMPOSIO_USER_ID tells Composio which user this session belongs to
  • OPENAI_API_KEY lets the Mastra agent call OpenAI models

Import libraries and validate environment

typescript
import "dotenv/config";
import { openai } from "@ai-sdk/openai";
import { Agent } from "@mastra/core/agent";
import { MCPClient } from "@mastra/mcp";
import { Composio } from "@composio/core";
import * as readline from "readline";

import type { AiMessageType } from "@mastra/core/agent";

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

if (!openaiAPIKey) 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 as string,
});
What's happening:
  • dotenv/config auto loads your .env so process.env.* is available
  • openai gives you a Mastra compatible model wrapper
  • Agent is the Mastra agent that will call tools and produce answers
  • MCPClient connects Mastra to your Composio MCP server
  • Composio is used to create a Tool Router session

Create a Tool Router session for Gmail

typescript
async function main() {
  const session = await composio.create(
    composioUserID as string,
    {
      toolkits: ["gmail"],
    },
  );

  const composioMCPUrl = session.mcp.url;
  console.log("Gmail MCP URL:", composioMCPUrl);
What's happening:
  • create spins up a short-lived MCP HTTP endpoint for this user
  • The toolkits array contains "gmail" for Gmail access
  • session.mcp.url is the MCP URL that Mastra's MCPClient will connect to

Configure Mastra MCP client and fetch tools

typescript
const mcpClient = new MCPClient({
    id: composioUserID as string,
    servers: {
      nasdaq: {
        url: new URL(composioMCPUrl),
        requestInit: {
          headers: session.mcp.headers,
        },
      },
    },
    timeout: 30_000,
  });

console.log("Fetching MCP tools from Composio...");
const composioTools = await mcpClient.getTools();
console.log("Number of tools:", Object.keys(composioTools).length);
What's happening:
  • MCPClient takes an id for this client and a list of MCP servers
  • The headers property includes the x-api-key for authentication
  • getTools fetches the tool definitions exposed by the Gmail toolkit

Create the Mastra agent

typescript
const agent = new Agent({
    name: "gmail-mastra-agent",
    instructions: "You are an AI agent with Gmail tools via Composio.",
    model: "openai/gpt-5",
  });
What's happening:
  • Agent is the core Mastra agent
  • name is just an identifier for logging and debugging
  • instructions guide the agent to use tools instead of only answering in natural language
  • model uses openai("gpt-5") to configure the underlying LLM

Set up interactive chat interface

typescript
let messages: AiMessageType[] = [];

console.log("Chat started! Type 'exit' or 'quit' to end.\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({
    id: crypto.randomUUID(),
    role: "user",
    content: trimmedInput,
  });

  console.log("\nAgent is thinking...\n");

  try {
    const response = await agent.generate(messages, {
      toolsets: {
        gmail: composioTools,
      },
      maxSteps: 8,
    });

    const { text } = response;

    if (text && text.trim().length > 0) {
      console.log(`Agent: ${text}\n`);
        messages.push({
          id: crypto.randomUUID(),
          role: "assistant",
          content: text,
        });
      }
    } catch (error) {
      console.error("\nError:", error);
    }

    rl.prompt();
  });

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

main().catch((err) => {
  console.error("Fatal error:", err);
  process.exit(1);
});
What's happening:
  • messages keeps the full conversation history in Mastra's expected format
  • agent.generate runs the agent with conversation history and Gmail toolsets
  • maxSteps limits how many tool calls the agent can take in a single run
  • onStepFinish is a hook that prints intermediate steps for debugging

Complete Code

Here's the complete code to get you started with Gmail and Mastra AI:

typescript
import "dotenv/config";
import { openai } from "@ai-sdk/openai";
import { Agent } from "@mastra/core/agent";
import { MCPClient } from "@mastra/mcp";
import { Composio } from "@composio/core";
import * as readline from "readline";

import type { AiMessageType } from "@mastra/core/agent";

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

if (!openaiAPIKey) 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 as string });

async function main() {
  const session = await composio.create(composioUserID as string, {
    toolkits: ["gmail"],
  });

  const composioMCPUrl = session.mcp.url;

  const mcpClient = new MCPClient({
    id: composioUserID as string,
    servers: {
      gmail: {
        url: new URL(composioMCPUrl),
        requestInit: {
          headers: session.mcp.headers,
        },
      },
    },
    timeout: 30_000,
  });

  const composioTools = await mcpClient.getTools();

  const agent = new Agent({
    name: "gmail-mastra-agent",
    instructions: "You are an AI agent with Gmail tools via Composio.",
    model: "openai/gpt-5",
  });

  let messages: AiMessageType[] = [];

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

  rl.prompt();

  rl.on("line", async (input: string) => {
    const trimmed = input.trim();
    if (["exit", "quit"].includes(trimmed.toLowerCase())) {
      rl.close();
      return;
    }

    messages.push({ id: crypto.randomUUID(), role: "user", content: trimmed });

    const { text } = await agent.generate(messages, {
      toolsets: { gmail: composioTools },
      maxSteps: 8,
    });

    if (text) {
      console.log(`Agent: ${text}\n`);
      messages.push({ id: crypto.randomUUID(), role: "assistant", content: text });
    }

    rl.prompt();
  });

  rl.on("close", async () => {
    await mcpClient.disconnect();
    process.exit(0);
  });
}

main();

Conclusion

You've built a Mastra AI agent that can interact with Gmail through Composio's Tool Router. You can extend this further by:
  • Adding other toolkits like Gmail, Slack, or GitHub
  • Building a web-based chat interface around this agent
  • Using multiple MCP endpoints to enable cross-app workflows

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FAQ

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

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

Can I use Tool Router MCP with Mastra AI?

Yes, you can. Mastra 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 Gmail tools.

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

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

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