How to integrate Resend MCP with Google ADK

This guide walks you through connecting Resend to Google ADK using the Composio tool router. By the end, you'll have a working Resend agent that can create a new contact for your newsletter, list all domains connected to your account, cancel a scheduled marketing email through natural language commands. This guide will help you understand how to give your Google ADK agent real control over a Resend account through Composio's Resend MCP server. Before we dive in, let's take a quick look at the key ideas and tools involved.

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Resend

Api Key

Resend is a universal API for sending emails using a single, modern endpoint. It streamlines transactional and marketing email delivery for developers and teams.

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Introduction

This guide will help you understand how to give your Google ADK agent real control over a Resend account through Composio's Resend MCP server.

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

Also integrate Resend with

OpenAI Agents SDK Claude Agent SDK Claude Code Claude Cowork Codex OpenClaw Hermes CLI LangChain Vercel AI SDK Mastra AI LlamaIndex CrewAI

TL;DR

Here's what you'll learn:

Get a Resend account set up and connected to Composio
Install the Google ADK and Composio packages
Create a Composio Tool Router session for Resend
Build an agent that connects to Resend through MCP
Interact with Resend using natural language

What is Google ADK?

Google ADK (Agents Development Kit) is Google's framework for building AI agents powered by Gemini models. It provides tools for creating agents that can use external services through the Model Context Protocol.

Key features include:

Gemini Integration: Native support for Google's Gemini models
MCP Toolset: Built-in support for Model Context Protocol tools
Streamable HTTP: Connect to external services through streamable HTTP
CLI and Web UI: Run agents via command line or web interface

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

The Resend MCP server is an implementation of the Model Context Protocol that connects your AI agent and assistants like Claude, Cursor, etc directly to your Resend account. It provides structured and secure access to your email sending and contact management capabilities, so your agent can perform actions like sending emails, managing audiences, creating domains, and handling contacts on your behalf.

Automated email delivery and scheduling: Ask your agent to send emails instantly or schedule them for later, and even cancel scheduled messages if needed.
Audience and contact management: Let your agent create, list, or delete audiences and individual contacts, keeping your recipient lists organized without manual effort.
Domain administration: Easily have your agent set up, list, or remove email sending domains, streamlining onboarding or maintenance for your email infrastructure.
Seamless recipient segmentation: Direct your agent to group contacts into audiences for targeted campaigns or communications, improving personalization and reach.
Bulk operations and cleanups: Enable your agent to quickly list, update, or delete multiple contacts, audiences, or domains to maintain a tidy and up-to-date email system.

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:

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

Step-by-step Guide

Step by step09 STEPS

Prerequisites

Before starting, make sure you have:

A Google API key for Gemini models
A Composio account and API key
Python 3.9 or later installed
Basic familiarity with Python

Getting API Keys for Google and Composio

Google API Key

Go to Google AI Studio and create an API key.
Copy the key and keep it safe. You will put this in GOOGLE_API_KEY.

Composio API Key and User ID

Log in to the Composio dashboard.
Go to Settings → API Keys and copy your Composio API key. Use this for COMPOSIO_API_KEY.
Decide on a stable user identifier to scope sessions, often your email or a user ID. Use this for COMPOSIO_USER_ID.

Install dependencies

bash

pip install google-adk composio python-dotenv

Inside your virtual environment, install the required packages.

What's happening:

google-adk is Google's Agents Development Kit
composio connects your agent to Resend via MCP
python-dotenv loads environment variables

Set up ADK project

bash

adk create my_agent

Set up a new Google ADK project.

What's happening:

This creates an agent folder with a root agent file and .env file

Set environment variables

bash

GOOGLE_API_KEY=your-google-api-key
COMPOSIO_API_KEY=your-composio-api-key
COMPOSIO_USER_ID=your-user-id-or-email

Save all your credentials in the .env file.

What's happening:

GOOGLE_API_KEY authenticates with Google's Gemini models
COMPOSIO_API_KEY authenticates with Composio
COMPOSIO_USER_ID identifies the user for session management

Import modules and validate environment

python

import os
import warnings

from composio import Composio
from dotenv import load_dotenv
from google.adk.agents.llm_agent import Agent
from google.adk.tools.mcp_tool.mcp_session_manager import StreamableHTTPConnectionParams
from google.adk.tools.mcp_tool.mcp_toolset import McpToolset

load_dotenv()

warnings.filterwarnings("ignore", message=".*BaseAuthenticatedTool.*")

GOOGLE_API_KEY = os.getenv("GOOGLE_API_KEY")
COMPOSIO_API_KEY = os.getenv("COMPOSIO_API_KEY")
COMPOSIO_USER_ID = os.getenv("COMPOSIO_USER_ID")

if not GOOGLE_API_KEY:
    raise ValueError("GOOGLE_API_KEY is not set in the environment.")
if not COMPOSIO_API_KEY:
    raise ValueError("COMPOSIO_API_KEY is not set in the environment.")
if not COMPOSIO_USER_ID:
    raise ValueError("COMPOSIO_USER_ID is not set in the environment.")

What's happening:

os reads environment variables
Composio is the main Composio SDK client
GoogleProvider declares that you are using Google ADK as the agent runtime
Agent is the Google ADK LLM agent class
McpToolset lets the ADK agent call MCP tools over HTTP

Create Composio client and Tool Router session

python

composio_client = Composio(api_key=COMPOSIO_API_KEY)

composio_session = composio_client.create(
    user_id=COMPOSIO_USER_ID,
    toolkits=["resend"],
)

COMPOSIO_MCP_URL = composio_session.mcp.url,
print(f"Composio MCP URL: {COMPOSIO_MCP_URL}")

What's happening:

Authenticates to Composio with your API key
Declares Google ADK as the provider
Spins up a short-lived MCP endpoint for your user and selected toolkit
Stores the MCP HTTP URL for the ADK MCP integration

Set up the McpToolset and create the Agent

python

composio_toolset = McpToolset(
    connection_params=StreamableHTTPConnectionParams(
        url=COMPOSIO_MCP_URL,
        headers={"x-api-key": COMPOSIO_API_KEY}
    )
)

root_agent = Agent(
    model="gemini-2.5-flash",
    name="composio_agent",
    description="An agent that uses Composio tools to perform actions.",
    instruction=(
        "You are a helpful assistant connected to Composio. "
        "You have the following tools available: "
        "COMPOSIO_SEARCH_TOOLS, COMPOSIO_MULTI_EXECUTE_TOOL, "
        "COMPOSIO_MANAGE_CONNECTIONS, COMPOSIO_REMOTE_BASH_TOOL, COMPOSIO_REMOTE_WORKBENCH. "
        "Use these tools to help users with Resend operations."
    ),
    tools=[composio_toolset],
)

print("\nAgent setup complete. You can now run this agent directly ;)")

What's happening:

Connects the ADK agent to the Composio MCP endpoint through McpToolset
Uses Gemini as the model powering the agent
Lists exact tool names in instruction to reduce misnamed tool calls

Run the agent

bash

# Run in CLI mode
adk run my_agent

# Or run in web UI mode
adk web

Execute the agent from the project root. The web command opens a web portal where you can chat with the agent.

What's happening:

adk run runs the agent in CLI mode
adk web . opens a web UI for interactive testing

Complete Code

Here's the complete code to get you started with Resend and Google ADK:

python

import os
import warnings

from composio import Composio
from composio_google import GoogleProvider
from dotenv import load_dotenv
from google.adk.agents.llm_agent import Agent
from google.adk.tools.mcp_tool.mcp_session_manager import StreamableHTTPConnectionParams
from google.adk.tools.mcp_tool.mcp_toolset import McpToolset

load_dotenv()
warnings.filterwarnings("ignore", message=".*BaseAuthenticatedTool.*")

GOOGLE_API_KEY = os.getenv("GOOGLE_API_KEY")
COMPOSIO_API_KEY = os.getenv("COMPOSIO_API_KEY")
COMPOSIO_USER_ID = os.getenv("COMPOSIO_USER_ID")

if not GOOGLE_API_KEY:
    raise ValueError("GOOGLE_API_KEY is not set in the environment.")
if not COMPOSIO_API_KEY:
    raise ValueError("COMPOSIO_API_KEY is not set in the environment.")
if not COMPOSIO_USER_ID:
    raise ValueError("COMPOSIO_USER_ID is not set in the environment.")

composio_client = Composio(api_key=COMPOSIO_API_KEY, provider=GoogleProvider())

composio_session = composio_client.create(
    user_id=COMPOSIO_USER_ID,
    toolkits=["resend"],
)

COMPOSIO_MCP_URL = composio_session.mcp.url


composio_toolset = McpToolset(
    connection_params=StreamableHTTPConnectionParams(
        url=COMPOSIO_MCP_URL,
        headers={"x-api-key": COMPOSIO_API_KEY}
    )
)

root_agent = Agent(
    model="gemini-2.5-flash",
    name="composio_agent",
    description="An agent that uses Composio tools to perform actions.",
    instruction=(
        "You are a helpful assistant connected to Composio. "
        "You have the following tools available: "
        "COMPOSIO_SEARCH_TOOLS, COMPOSIO_MULTI_EXECUTE_TOOL, "
        "COMPOSIO_MANAGE_CONNECTIONS, COMPOSIO_REMOTE_BASH_TOOL, COMPOSIO_REMOTE_WORKBENCH. "
        "Use these tools to help users with Resend operations."
    ),  
    tools=[composio_toolset],
)

print("\nAgent setup complete. You can now run this agent directly ;)")

Conclusion

You've successfully integrated Resend with the Google ADK through Composio's MCP Tool Router. Your agent can now interact with Resend using natural language commands.

Key takeaways:

The Tool Router approach dynamically routes requests to the appropriate Resend tools
Environment variables keep your credentials secure and separate from code
Clear agent instructions reduce tool calling errors
The ADK web UI provides an interactive interface for testing and development

You can extend this setup by adding more toolkits to the toolkits array in your session configuration.

TOOLS

Supported Tools

Every Resend action and event your agent gets out of the box.

Add Contact To Segment

Add an existing contact to a segment in Resend.

Cancel Email

Cancel a scheduled email.

Create API Key

Create a new API key to authenticate communications with Resend.

Create Audience

Create a list of contacts.

Create Contact

Create a contact in Resend.

Create Contact Property

Tool to create a new contact property in Resend.

Create Contact V2

Tool to create a new contact in Resend.

Create Domain

Create a domain through the Resend Email API.

Create Template

Tool to create a new email template in Resend.

Create Topic

Tool to create a new topic to segment your audience.

Create Webhook

Tool to create a webhook to receive real-time notifications about email events.

Delete API Key

Remove an existing API key from Resend.

Delete Audience

Remove an existing audience.

Delete Contact

Delete a contact in Resend.

Delete Contact By ID

Tool to remove an existing contact by its ID.

Delete Contact Property

Remove an existing contact property from Resend.

Delete Domain

Delete a domain through the Resend Email API.

Delete Segment

Remove an existing segment.

Delete Template

Remove an existing template.

Delete Topic

Tool to remove an existing topic in Resend.

Delete Webhook

Remove an existing webhook.

Duplicate Template

Duplicate an existing template through the Resend Email API.

Get Contact

Tool to retrieve a single contact from Resend by ID or email.

Get Contact Property

Tool to retrieve a single contact property from Resend.

Get Email Attachment

Retrieve a single attachment from a sent email.

Get Segment

Retrieve a single segment by its ID.

Get Template

Retrieve a single template by ID or alias from Resend.

Get Topic

Tool to retrieve a single topic by its ID in Resend.

Get Webhook

Retrieve a single webhook for the authenticated user.

List All Contacts

Tool to retrieve a list of all contacts from Resend.

List API Keys

Tool to retrieve a list of API keys for the authenticated user.

List Audiences

List all audiences.

List Broadcasts

Tool to retrieve a list of broadcasts.

List Contact Properties

Tool to retrieve a list of contact properties from Resend.

List Contacts

List contacts in Resend.

List Contact Segments

Retrieve a list of segments that a contact is part of.

List Contact Topics

Retrieve a list of topic subscriptions for a contact in Resend.

List Domains

List all domains.

List Email Attachments

Tool to retrieve a list of attachments from a sent email.

List Emails

Tool to retrieve a list of emails sent by your team.

List Received Emails

Tool to retrieve a list of received emails for the authenticated user.

List Segments

Tool to retrieve a list of segments from Resend.

List Templates

Tool to retrieve a list of templates from Resend.

List Topics

Tool to retrieve a list of topics for the authenticated user.

List Webhooks

Retrieve a list of webhooks for the authenticated user.

Publish Template

Publish a template through the Resend Email API.

Remove Contact From Segment

Remove an existing contact from a segment.

Retrieve Audience

Retrieve a single audience.

Retrieve Contact

Retrieve a contact in Resend.

Retrieve Domain

Retrieve a single domain.

Retrieve Email

Retrieve a single email.

Send Batch Emails

Trigger up to 100 batch emails at once.

Send Email

Send an email using Resend.

Update Broadcast

Update an existing broadcast in Resend.

Update Contact

Tool to update an existing contact in Resend by ID or email.

Update Contact Property

Update an existing contact property in Resend.

Update Domain

Update an existing domain.

Update Email

Update a scheduled email.

Update Template

Tool to update an existing email template in Resend.

Update Topic

Tool to update an existing topic in Resend.

Update Webhook

Tool to update an existing webhook configuration.

Verify Domain

Verify a domain through the Resend Email API.

FRAMEWORKS

How to build Resend MCP Agent with another framework

OpenAI Agents SDK

Use Resend MCP with OpenAI Agents SDK

Claude Agent SDK

Use Resend MCP with Claude Agent SDK

Claude Code

Use Resend MCP with Claude Code

Claude Cowork

Use Resend MCP with Claude Cowork

Codex

Use Resend MCP with Codex

OpenClaw

Use Resend MCP with OpenClaw

Hermes

Use Resend MCP with Hermes

CLI

Use Resend MCP with CLI

LangChain

Use Resend MCP with LangChain

Vercel AI SDK

Use Resend MCP with Vercel AI SDK

Mastra AI

Use Resend MCP with Mastra AI

LlamaIndex

Use Resend MCP with LlamaIndex

CrewAI

Use Resend MCP with CrewAI

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FAQ

Frequently asked questions

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

Yes, you can. Google ADK 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 Resend tools.

Yes, absolutely. You can configure which Resend 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.

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 Resend data and credentials are handled as safely as possible.

Start with Resend.It takes 30 seconds.

Managed auth, hosted MCP servers, and every Resend tool your agent needs.Free to start.

Start building

Customer stories

Teams ship real agents on Composio

GET STARTED FOR FREE BOOK A DEMO

Karan skipped his own birthday party to fix our critical issue. It was 10pm and he diverted his Waymo to help us instead. This really sets the bar — it shows the commitment you need when users rely on your software.

Harsha Gaddipati

Co-founder, Slashy

A lot of students tell us that the moment their connected tools start talking to each other inside Opennote feels almost magical. The agent just knows them, and it's immensely helped keep new users on the platform.

Abhi Arya

Co-founder, Opennote

We chose Composio over Pipedream because it delivered depth where it mattered — niche tools and tricky edge cases other platforms simply ignored. That gave us confidence to scale without compromising.

Nirman Dave

CEO, Zams

As a solo builder, shipping fast is life or death. The only way I can outcompete incumbents is by outmanoeuvring them. Getting bogged down managing agent auth would have been a death sentence.

Ryan Yu

Founder, Extra Thursday

Before Composio, adding tool integrations was slow and resource-intensive. Each one could take weeks of engineering time, and maintaining them meant constantly keeping up with API changes.

Tomisin Jenrola

Founder & CEO, SwarmZero

With hands-on help from their founder, we integrated Gmail and Google Drive in just 30 minutes. This level of personal support and commitment is exactly what startups should strive for.

Jerome Leclanche

Co-Founder, Ingram Technologies

How to integrate Resend MCP with Google ADK

Connect Resend without auth hassles

Introduction

Also integrate Resend with

TL;DR

What is Google ADK?

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

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

What is Composio SDK?

How the Composio SDK works

Step-by-step Guide

Prerequisites

Getting API Keys for Google and Composio

Install dependencies

Set up ADK project

Set environment variables

Import modules and validate environment

Create Composio client and Tool Router session

Set up the McpToolset and create the Agent

Run the agent

Complete Code

Conclusion

Supported Tools

How to build Resend MCP Agent with another framework

OpenAI Agents SDK

Claude Agent SDK

Claude Code

Claude Cowork

Codex

OpenClaw

Hermes

CLI

LangChain

Vercel AI SDK

Mastra AI

LlamaIndex

CrewAI

Explore Other Toolkits

Reddit

Facebook

Linkedin

Active campaign

Frequently asked questions

What are the differences in Tool Router MCP and Resend MCP?+

Can I use Tool Router MCP with Google ADK?+

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

How safe is my data with Composio Tool Router?+

Start with Resend.It takes 30 seconds.

Teams ship real agents on Composio