How to integrate Resend MCP with Pydantic AI

This guide walks you through connecting Resend to Pydantic AI 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 Pydantic AI 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 Pydantic AI 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 Google ADK LangChain Vercel AI SDK Mastra AI LlamaIndex CrewAI

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 Resend
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 Resend 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 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:

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 Resend
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 Resend
MCPServerStreamableHTTP connects to the Resend 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 Resend
    composio = Composio(api_key=api_key)
    session = composio.create(
        user_id=user_id,
        toolkits=["resend"],
    )
    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 Resend 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
resend_mcp = MCPServerStreamableHTTP(url, headers={"x-api-key": COMPOSIO_API_KEY})
agent = Agent(
    "openai:gpt-5",
    toolsets=[resend_mcp],
    instructions=(
        "You are a Resend assistant. Use Resend tools to help users "
        "with their requests. Ask clarifying questions when needed."
    ),
)

What's happening:

The MCP client connects to the Resend endpoint
The agent uses GPT-5 to interpret user commands and perform Resend 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 Resend.\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
Resend 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 Resend 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 Resend
    composio = Composio(api_key=api_key)
    session = composio.create(
        user_id=user_id,
        toolkits=["resend"],
    )
    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
    resend_mcp = MCPServerStreamableHTTP(url, headers={"x-api-key": COMPOSIO_API_KEY})
    agent = Agent(
        "openai:gpt-5",
        toolsets=[resend_mcp],
        instructions=(
            "You are a Resend assistant. Use Resend 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 Resend.\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 Resend through Composio's Tool Router. With this setup, your agent can perform real Resend 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 + Resend for workflow automation)

This architecture makes your AI agent "agent-native", able to securely use APIs in a unified, composable way without custom integrations.

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

Google ADK

Use Resend MCP with Google ADK

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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Active campaign

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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. 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 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 Pydantic AI

Connect Resend without auth hassles

Introduction

Also integrate Resend with

TL;DR

What is Pydantic AI?

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 OpenAI and Composio

Install dependencies

Set up environment variables

Import dependencies

Create a Tool Router Session

Initialize the Pydantic AI Agent

Build the chat interface

Run the application

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

Google ADK

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 Pydantic AI?+

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