How to integrate Lemon squeezy MCP with LangChain

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Introduction

This guide walks you through connecting Lemon squeezy to LangChain using the Composio tool router. By the end, you'll have a working Lemon squeezy agent that can list all recent orders for my store, create a new customer with email address, show all active discounts available now, list all affiliates and their details through natural language commands.

This guide will help you understand how to give your LangChain agent real control over a Lemon squeezy account through Composio's Lemon squeezy 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:
  • Get and set up your OpenAI and Composio API keys
  • Connect your Lemon squeezy project to Composio
  • Create a Tool Router MCP session for Lemon squeezy
  • Initialize an MCP client and retrieve Lemon squeezy tools
  • Build a LangChain agent that can interact with Lemon squeezy
  • Set up an interactive chat interface for testing

What is LangChain?

LangChain is a framework for developing applications powered by language models. It provides tools and abstractions for building agents that can reason, use tools, and maintain conversation context.

Key features include:

  • Agent Framework: Build agents that can use tools and make decisions
  • MCP Integration: Connect to external services through Model Context Protocol adapters
  • Memory Management: Maintain conversation history across interactions
  • Multi-Provider Support: Works with OpenAI, Anthropic, and other LLM providers

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

The Lemon Squeezy MCP server is an implementation of the Model Context Protocol that connects your AI agent and assistants like Claude, Cursor, etc directly to your Lemon Squeezy account. It provides structured and secure access to your e-commerce operations, so your agent can perform actions like managing customers, tracking orders, retrieving discounts, and handling subscriptions on your behalf.

  • Customer creation and management: Quickly add new customers or pull up detailed customer lists, streamlining your onboarding and support flows.
  • Order tracking and retrieval: Effortlessly fetch a paginated list of orders or drill down to specific order items to monitor sales activity and fulfillment status.
  • Discount and affiliate insights: Retrieve all active discounts or affiliate partners, making it a breeze to analyze promotions and partner performance.
  • Checkout and price listing: Access and filter all checkouts or prices across your stores and variants, helping you keep tabs on your sales funnels and product offerings.
  • License key and redemption management: List all license key instances and track discount redemptions, ensuring easy oversight of software access and promotional usage.

Supported Tools & Triggers

Tools
Create CustomerTool to create a new customer.
List All AffiliatesTool to list all affiliates.
List All CheckoutsTool to list all checkouts.
List All CustomersTool to list all customers.
List All Discount RedemptionsTool to list all discount redemptions.
List All DiscountsTool to list all discounts.
List All License Key InstancesTool to list all license key instances.
List All Order ItemsTool to list all order items.
List All OrdersTool to list all orders.
List All PricesTool to list all prices.
List All ProductsTool to list all products.
List All StoresTool to list all stores.
List All Subscription InvoicesTool to list all subscription invoices.
List All Subscription ItemsTool to list all subscription items.
List All SubscriptionsTool to list all subscriptions.
List All Usage RecordsTool to list all usage records.
List All VariantsTool to list all variants.
List All WebhooksTool to list all webhooks.

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 starting this tutorial, make sure you have:
  • Python 3.10 or higher installed on your system
  • A Composio account with an API key
  • An OpenAI 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

pip install composio-langchain langchain-mcp-adapters langchain python-dotenv

Install the required packages for LangChain with MCP support.

What's happening:

  • composio-langchain provides Composio integration for LangChain
  • langchain-mcp-adapters enables MCP client connections
  • langchain is the core agent framework
  • python-dotenv loads environment variables

Set up environment variables

bash
COMPOSIO_API_KEY=your_composio_api_key_here
COMPOSIO_USER_ID=your_composio_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's API
  • COMPOSIO_USER_ID identifies the user for session management
  • OPENAI_API_KEY enables access to OpenAI's language models

Import dependencies

from langchain_mcp_adapters.client import MultiServerMCPClient
from langchain.agents import create_agent
from dotenv import load_dotenv
from composio import Composio
import asyncio
import os

load_dotenv()
What's happening:
  • We're importing LangChain's MCP adapter and Composio SDK
  • The dotenv import loads environment variables from your .env file
  • This setup prepares the foundation for connecting LangChain with Lemon squeezy functionality through MCP

Initialize Composio client

async def main():
    composio = Composio(api_key=os.getenv("COMPOSIO_API_KEY"))

    if not os.getenv("COMPOSIO_API_KEY"):
        raise ValueError("COMPOSIO_API_KEY is not set")
    if not os.getenv("COMPOSIO_USER_ID"):
        raise ValueError("COMPOSIO_USER_ID is not set")
What's happening:
  • We're loading the COMPOSIO_API_KEY from environment variables and validating it exists
  • Creating a Composio instance that will manage our connection to Lemon squeezy tools
  • Validating that COMPOSIO_USER_ID is also set before proceeding

Create a Tool Router session

# Create Tool Router session for Lemon squeezy
session = composio.create(
    user_id=os.getenv("COMPOSIO_USER_ID"),
    toolkits=['lemon_squeezy']
)

url = session.mcp.url
What's happening:
  • We're creating a Tool Router session that gives your agent access to Lemon squeezy 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
  • This approach allows the agent to dynamically load and use Lemon squeezy tools as needed

Configure the agent with the MCP URL

client = MultiServerMCPClient({
    "lemon_squeezy-agent": {
        "transport": "streamable_http",
        "url": session.mcp.url,
        "headers": {
            "x-api-key": os.getenv("COMPOSIO_API_KEY")
        }
    }
})

tools = await client.get_tools()

agent = create_agent("gpt-5", tools)
What's happening:
  • We're creating a MultiServerMCPClient that connects to our Lemon squeezy MCP server via HTTP
  • The client is configured with a name and the URL from our Tool Router session
  • get_tools() retrieves all available Lemon squeezy tools that the agent can use
  • We're creating a LangChain agent using the GPT-5 model

Set up interactive chat interface

conversation_history = []

print("Chat started! Type 'exit' or 'quit' to end the conversation.\n")
print("Ask any Lemon squeezy related question or task to the agent.\n")

while True:
    user_input = input("You: ").strip()

    if user_input.lower() in ['exit', 'quit', 'bye']:
        print("\nGoodbye!")
        break

    if not user_input:
        continue

    conversation_history.append({"role": "user", "content": user_input})
    print("\nAgent is thinking...\n")

    response = await agent.ainvoke({"messages": conversation_history})
    conversation_history = response['messages']
    final_response = response['messages'][-1].content
    print(f"Agent: {final_response}\n")
What's happening:
  • We initialize an empty conversation_history list to maintain context across interactions
  • A while loop continuously accepts user input from the command line
  • When a user types a message, it's added to the conversation history and sent to the agent
  • The agent processes the request using the ainvoke() method with the full conversation history
  • Users can type 'exit', 'quit', or 'bye' to end the chat session gracefully

Run the application

if __name__ == "__main__":
    asyncio.run(main())
What's happening:
  • We call the main() function using asyncio.run() to start the application

Complete Code

Here's the complete code to get you started with Lemon squeezy and LangChain:

from langchain_mcp_adapters.client import MultiServerMCPClient
from langchain.agents import create_agent
from dotenv import load_dotenv
from composio import Composio
import asyncio
import os

load_dotenv()

async def main():
    composio = Composio(api_key=os.getenv("COMPOSIO_API_KEY"))
    
    if not os.getenv("COMPOSIO_API_KEY"):
        raise ValueError("COMPOSIO_API_KEY is not set")
    if not os.getenv("COMPOSIO_USER_ID"):
        raise ValueError("COMPOSIO_USER_ID is not set")
    
    session = composio.create(
        user_id=os.getenv("COMPOSIO_USER_ID"),
        toolkits=['lemon_squeezy']
    )

    url = session.mcp.url
    
    client = MultiServerMCPClient({
        "lemon_squeezy-agent": {
            "transport": "streamable_http",
            "url": url,
            "headers": {
                "x-api-key": os.getenv("COMPOSIO_API_KEY")
            }
        }
    })
    
    tools = await client.get_tools()
  
    agent = create_agent("gpt-5", tools)
    
    conversation_history = []
    
    print("Chat started! Type 'exit' or 'quit' to end the conversation.\n")
    print("Ask any Lemon squeezy related question or task to the agent.\n")
    
    while True:
        user_input = input("You: ").strip()
        
        if user_input.lower() in ['exit', 'quit', 'bye']:
            print("\nGoodbye!")
            break
        
        if not user_input:
            continue
        
        conversation_history.append({"role": "user", "content": user_input})
        print("\nAgent is thinking...\n")
        
        response = await agent.ainvoke({"messages": conversation_history})
        conversation_history = response['messages']
        final_response = response['messages'][-1].content
        print(f"Agent: {final_response}\n")

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

Conclusion

You've successfully built a LangChain agent that can interact with Lemon squeezy through Composio's Tool Router.

Key features of this implementation:

  • Dynamic tool loading through Composio's Tool Router
  • Conversation history maintenance for context-aware responses
  • Async Python provides clean, efficient execution of agent workflows
You can extend this further by adding error handling, implementing specific business logic, or integrating additional Composio toolkits to create multi-app workflows.

How to build Lemon squeezy MCP Agent with another framework

OpenAI Agents SDK

OpenAI Agents SDK

Use Lemon squeezy MCP with OpenAI Agents SDK

Claude Agent SDK

Claude Agent SDK

Use Lemon squeezy MCP with Claude Agent SDK

Google ADK

Google ADK

Use Lemon squeezy MCP with Google ADK

Vercel AI SDK

Vercel AI SDK

Use Lemon squeezy MCP with Vercel AI SDK

Mastra AI

Mastra AI

Use Lemon squeezy MCP with Mastra AI

LlamaIndex

LlamaIndex

Use Lemon squeezy MCP with LlamaIndex

CrewAI

CrewAI

Use Lemon squeezy MCP with CrewAI

FAQ

What are the differences in Tool Router MCP and Lemon squeezy MCP?

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

Can I use Tool Router MCP with LangChain?

Yes, you can. LangChain 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 Lemon squeezy tools.

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

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

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