How to integrate Bigmailer MCP with Claude Agent SDK

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Introduction

This guide walks you through connecting Bigmailer to the Claude Agent SDK using the Composio tool router. By the end, you'll have a working Bigmailer agent that can create a new welcome campaign for brand x, list all brands i manage in bigmailer, get your bigmailer account user details through natural language commands.

This guide will help you understand how to give your Claude Agent SDK agent real control over a Bigmailer account through Composio's Bigmailer MCP server.

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

Also integrate Bigmailer with

TL;DR

Here's what you'll learn:
  • Get and set up your Claude/Anthropic and Composio API keys
  • Install the necessary dependencies
  • Initialize Composio and create a Tool Router session for Bigmailer
  • Configure an AI agent that can use Bigmailer as a tool
  • Run a live chat session where you can ask the agent to perform Bigmailer operations

What is Claude Agent SDK?

The Claude Agent SDK is Anthropic's official framework for building AI agents powered by Claude. It provides a streamlined interface for creating agents with MCP tool support and conversation management.

Key features include:

  • Native MCP Support: Built-in support for Model Context Protocol servers
  • Permission Modes: Control tool execution permissions
  • Streaming Responses: Real-time response streaming for interactive applications
  • Context Manager: Clean async context management for sessions

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

The Bigmailer MCP server is an implementation of the Model Context Protocol that connects your AI agent and assistants like Claude, Cursor, etc directly to your Bigmailer account. It provides structured and secure access to your email marketing platform, so your agent can perform actions like creating transactional campaigns, retrieving your brands, and managing user account details on your behalf.

  • Automated transactional campaign creation: Have your agent quickly set up new transactional email campaigns for any of your brands, with full control over content, sender details, and subject lines.
  • Brand management and discovery: Let your agent list and organize all brands associated with your Bigmailer account, providing a clear overview for multi-brand operations.
  • User account information retrieval: Easily check your authenticated user details to verify API connectivity and view essential account information in real time.
  • Multi-brand marketing workflow automation: Empower your agent to streamline campaign launches and brand management across multiple business entities from one place.

Supported Tools & Triggers

Tools
Create BrandTool to create a new brand in BigMailer.
Create Brand PropertyTool to create a brand property in BigMailer.
Create Bulk CampaignTool to create a bulk email campaign in BigMailer.
Create ContactTool to create a new contact in BigMailer within a specified brand.
Create Contact BatchTool to create a batch of contacts in BigMailer for a specific brand.
Create FieldTool to create a custom field in a BigMailer brand.
Create ListCreates a new contact list within a specified brand in BigMailer.
Create SegmentTool to create a segment in BigMailer for a specific brand.
Create Suppression ListTool to upload a suppression list for a brand in BigMailer.
Create TemplateTool to create a new email or page template in BigMailer.
Create Transactional CampaignCreates a new transactional campaign within a specified brand in BigMailer.
Create UserTool to create a new user in BigMailer.
Delete Brand PropertyTool to delete a brand property from a brand in BigMailer.
Delete ContactTool to delete a contact from a brand in BigMailer.
Delete Custom FieldDeletes a custom field from a specified brand in BigMailer.
Delete ListTool to delete a list from BigMailer.
Delete SegmentTool to delete a segment from a brand in BigMailer.
Delete TemplateTool to delete a template from BigMailer.
Delete UserTool to delete a user from BigMailer.
Get BrandTool to retrieve detailed information about a specific brand by its ID.
Get Brand PropertyTool to retrieve a specific brand property by its ID for a given brand.
Get Bulk CampaignTool to retrieve detailed information about a specific bulk campaign in BigMailer.
Get ContactTool to retrieve detailed information about a specific contact from BigMailer.
Get Contact Batch StatusTool to retrieve the status and results of a contact batch upload in BigMailer.
Get Custom FieldTool to retrieve a custom field from a BigMailer brand.
Get ListTool to retrieve details of a specific list within a brand.
Get SegmentTool to retrieve a specific segment from BigMailer by brand ID and segment ID.
Get Suppression ListTool to retrieve details of a specific suppression list for a brand in BigMailer.
Get TemplateTool to retrieve detailed information about a specific template by its ID.
Get Transactional CampaignTool to retrieve detailed information about a specific transactional campaign in BigMailer.
Get UserTool to retrieve detailed information about a specific user by their ID.
Get User InformationThis tool retrieves information about the authenticated user in BigMailer using the GET /me endpoint.
List All BrandsThis tool retrieves a list of all brands associated with the authenticated BigMailer account.
List Brand PropertiesTool to retrieve a list of brand properties for a specific brand in BigMailer.
List Bulk CampaignsTool to list bulk campaigns for a specified brand in BigMailer.
List ConnectionsTool to list all connections in your BigMailer account.
List ContactsTool to list contacts for a brand in BigMailer.
List FieldsTool to list custom fields for a brand in BigMailer.
List Contact ListsTool to retrieve all contact lists for a specified brand in BigMailer.
List Message TypesTool to list message types for a specific brand in BigMailer.
List SegmentsTool to list segments for a brand in BigMailer.
List SendersTool to list all senders configured for a specific brand in BigMailer.
List Suppression ListsTool to list suppression lists for a specific brand.
List TemplatesTool to list templates for a brand in BigMailer.
List Transactional CampaignsTool to list transactional campaigns for a specified brand in BigMailer.
List UsersTool to list all users in your BigMailer account.
Update BrandTool to update a brand in BigMailer.
Update Brand PropertyTool to update a brand property in BigMailer.
Update Bulk CampaignTool to update an existing bulk campaign in BigMailer.
Update ContactTool to update an existing contact in BigMailer.
Update FieldTool to update a custom field in BigMailer.
Update ListTool to update a list in BigMailer.
Update SegmentTool to update an existing segment in BigMailer.
Update TemplateTool to update an existing email or page template in BigMailer.
Update Transactional CampaignTool to update a transactional campaign in BigMailer.
Update UserTool to update a user in BigMailer.
Upsert ContactTool to create or update a contact in a BigMailer brand.

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:
  • Composio API Key and Claude/Anthropic API Key
  • Primary know-how of Claude Agents SDK
  • A Bigmailer account
  • Some knowledge of Python

Getting API Keys for Claude/Anthropic and Composio

Claude/Anthropic API Key
  • Go to the Anthropic Console and create an API key. You'll need credits to use the models.
  • 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

pip install composio-anthropic claude-agent-sdk python-dotenv

Install the Composio SDK and the Claude Agents SDK.

What's happening:

  • composio-anthropic provides Composio integration for Anthropic
  • claude-agent-sdk is the core agent framework
  • python-dotenv loads environment variables

Set up environment variables

bash
COMPOSIO_API_KEY=your_composio_api_key_here
USER_ID=your_user_id_here
ANTHROPIC_API_KEY=your_anthropic_api_key_here

Create a .env file in your project root.

What's happening:

  • COMPOSIO_API_KEY authenticates with Composio
  • USER_ID identifies the user for session management
  • ANTHROPIC_API_KEY authenticates with Anthropic/Claude

Import dependencies

import asyncio
from claude_agent_sdk import ClaudeSDKClient, ClaudeAgentOptions
import os
from composio import Composio
from dotenv import load_dotenv

load_dotenv()
What's happening:
  • We're importing all necessary libraries including the Claude Agent SDK and Composio
  • The load_dotenv() function loads environment variables from your .env file
  • This setup prepares the foundation for connecting Claude with Bigmailer functionality

Create a Composio instance and Tool Router session

async def chat_with_remote_mcp():
    api_key = os.getenv("COMPOSIO_API_KEY")
    if not api_key:
        raise RuntimeError("COMPOSIO_API_KEY is not set")

    composio = Composio(api_key=api_key)

    # Create Tool Router session for Bigmailer
    mcp_server = composio.create(
        user_id=os.getenv("USER_ID"),
        toolkits=["bigmailer"]
    )

    url = mcp_server.mcp.url

    if not url:
        raise ValueError("Session URL not found")
What's happening:
  • The function checks for the required COMPOSIO_API_KEY environment variable
  • We're creating a Composio instance using our API key
  • The create method creates a Tool Router session for Bigmailer
  • The returned url is the MCP server URL that your agent will use

Configure Claude Agent with MCP

# Configure remote MCP server for Claude
options = ClaudeAgentOptions(
    permission_mode="bypassPermissions",
    mcp_servers={
        "composio": {
            "type": "http",
            "url": url,
            "headers": {
                "x-api-key": os.getenv("COMPOSIO_API_KEY")
            }
        }
    },
    system_prompt="You are a helpful assistant with access to Bigmailer tools via Composio.",
    max_turns=10
)
What's happening:
  • We're configuring the Claude Agent options with the MCP server URL
  • permission_mode="bypassPermissions" allows the agent to execute operations without asking for permission each time
  • The system prompt instructs the agent that it has access to Bigmailer
  • max_turns=10 limits the conversation length to prevent excessive API usage

Create client and start chat loop

# Create client with context manager
async with ClaudeSDKClient(options=options) as client:
    print("\nChat started. Type 'exit' or 'quit' to end.\n")

    # Main chat loop
    while True:
        user_input = input("You: ").strip()
        if user_input.lower() in {"exit", "quit"}:
            print("Goodbye!")
            break

        # Send query
        await client.query(user_input)

        # Receive and print response
        print("Claude: ", end="", flush=True)
        async for message in client.receive_response():
            if hasattr(message, "content"):
                for block in message.content:
                    if hasattr(block, "text"):
                        print(block.text, end="", flush=True)
        print()
What's happening:
  • The Claude SDK client is created using the async context manager pattern
  • The agent processes each query and streams the response back in real-time
  • The chat loop continues until the user types 'exit' or 'quit'

Run the application

if __name__ == "__main__":
    asyncio.run(chat_with_remote_mcp())
What's happening:
  • This entry point runs the async chat_with_remote_mcp() function using asyncio.run()
  • The application will start, create the MCP connection, and begin the interactive chat session

Complete Code

Here's the complete code to get you started with Bigmailer and Claude Agent SDK:

import asyncio
from claude_agent_sdk import ClaudeSDKClient, ClaudeAgentOptions
import os
from composio import Composio
from dotenv import load_dotenv

load_dotenv()

async def chat_with_remote_mcp():
    api_key = os.getenv("COMPOSIO_API_KEY")
    if not api_key:
        raise RuntimeError("COMPOSIO_API_KEY is not set")

    composio = Composio(api_key=api_key)

    # Create Tool Router session for Bigmailer
    mcp_server = composio.create(
        user_id=os.getenv("USER_ID"),
        toolkits=["bigmailer"]
    )

    url = mcp_server.mcp.url

    if not url:
        raise ValueError("Session URL not found")

    # Configure remote MCP server for Claude
    options = ClaudeAgentOptions(
        permission_mode="bypassPermissions",
        mcp_servers={
            "composio": {
                "type": "http",
                "url": url,
                "headers": {
                    "x-api-key": os.getenv("COMPOSIO_API_KEY")
                }
            }
        },
        system_prompt="You are a helpful assistant with access to Bigmailer tools via Composio.",
        max_turns=10
    )

    # Create client with context manager
    async with ClaudeSDKClient(options=options) as client:
        print("\nChat started. Type 'exit' or 'quit' to end.\n")

        # Main chat loop
        while True:
            user_input = input("You: ").strip()
            if user_input.lower() in {"exit", "quit"}:
                print("Goodbye!")
                break

            # Send query
            await client.query(user_input)

            # Receive and print response
            print("Claude: ", end="", flush=True)
            async for message in client.receive_response():
                if hasattr(message, "content"):
                    for block in message.content:
                        if hasattr(block, "text"):
                            print(block.text, end="", flush=True)
            print()

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

Conclusion

You've successfully built a Claude Agent SDK agent that can interact with Bigmailer through Composio's Tool Router.

Key features:

  • Native MCP support through Claude's agent framework
  • Streaming responses for real-time interaction
  • Permission bypass for smooth automated workflows
You can extend this by adding more toolkits, implementing custom business logic, or building a web interface around the agent.

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FAQ

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

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

Can I use Tool Router MCP with Claude Agent SDK?

Yes, you can. Claude Agent 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 Bigmailer tools.

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

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

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