How to integrate Lexoffice MCP with LangChain

This guide walks you through connecting Lexoffice to LangChain using the Composio tool router. By the end, you'll have a working Lexoffice agent that can generate and send new client invoices, summarize monthly expense reports, list overdue payments from customers through natural language commands. This guide will help you understand how to give your LangChain agent real control over a Lexoffice account through Composio's Lexoffice MCP server. Before we dive in, let's take a quick look at the key ideas and tools involved.

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Lexoffice is a cloud-based accounting platform for freelancers and small businesses. It streamlines invoicing, expense tracking, and integrates directly with your bank for hassle-free bookkeeping.

41 Tools

Introduction

This guide walks you through connecting Lexoffice to LangChain using the Composio tool router. By the end, you'll have a working Lexoffice agent that can generate and send new client invoices, summarize monthly expense reports, list overdue payments from customers through natural language commands.

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

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

Also integrate Lexoffice with

OpenAI Agents SDKClaude Agent SDKClaude CodeClaude CoworkCodexOpenClawHermesCLIGoogle ADKVercel AI SDKMastra AILlamaIndexCrewAI

TL;DR

Here's what you'll learn:
  • Get and set up your OpenAI and Composio API keys
  • Connect your Lexoffice project to Composio
  • Create a Tool Router MCP session for Lexoffice
  • Initialize an MCP client and retrieve Lexoffice tools
  • Build a LangChain agent that can interact with Lexoffice
  • 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 Lexoffice MCP server, and what's possible with it?

The Lexoffice MCP server is an implementation of the Model Context Protocol that connects your AI agent and assistants like Claude, Cursor, etc directly to your Lexoffice account. It provides structured and secure access to your Lexoffice workspace, so your agent can perform actions like managing invoices, tracking expenses, syncing with bank accounts, and handling client records on your behalf.

  • Invoice creation and management: Effortlessly generate, send, and track invoices, helping you streamline your billing process.
  • Expense tracking and categorization: Let your agent log and classify expenses, making it easy to stay on top of your business spending.
  • Bank integration and reconciliation: Automatically sync transactions with your connected bank accounts for simplified reconciliation and financial oversight.
  • Client and contact management: Manage your customer database, update records, and keep client information organized and up to date.
  • Financial reporting and insights: Generate detailed reports on your business’s financial health, including revenue, expenses, and outstanding balances.

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

Step by step10 STEPS
1

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
2

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.
3

Install dependencies

npm install @composio/langchain @langchain/core @langchain/openai @langchain/mcp-adapters 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/core is the core agent framework
  • dotenv/config loads environment variables
4

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
5

Import dependencies

import { Composio } from '@composio/core';
import { LangchainProvider } from '@composio/langchain';
import { MultiServerMCPClient } from "@langchain/mcp-adapters";
import { createAgent } from "langchain";
import * as readline from 'readline';
import 'dotenv/config';

dotenv.config();
What's happening:
  • We're importing LangChain's MCP adapter and Composio SDK
  • The dotenv/config import loads environment variables from your .env file
  • This setup prepares the foundation for connecting LangChain with Lexoffice functionality through MCP
6

Initialize Composio client

const composioApiKey = process.env.COMPOSIO_API_KEY;
const userId = process.env.COMPOSIO_USER_ID;

if (!composioApiKey) throw new Error('COMPOSIO_API_KEY is not set');
if (!userId) throw new Error('COMPOSIO_USER_ID is not set');

async function main() {
    const composio = new Composio({
        apiKey: composioApiKey as string,
        provider: new LangchainProvider()
    });
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 Lexoffice tools
  • Validating that COMPOSIO_USER_ID is also set before proceeding
7

Create a Tool Router session

const session = await composio.create(
    userId as string,
    {
        toolkits: ['lexoffice']
    }
);

const url = session.mcp.url;
What's happening:
  • We're creating a Tool Router session that gives your agent access to Lexoffice 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 Lexoffice tools as needed
8

Configure the agent with the MCP URL

const client = new MultiServerMCPClient({
    "lexoffice-agent": {
        transport: "http",
        url: url,
        headers: {
            "x-api-key": process.env.COMPOSIO_API_KEY
        }
    }
});

const tools = await client.getTools();

const agent = createAgent({ model: "gpt-5", tools });
What's happening:
  • We're creating a MultiServerMCPClient that connects to our Lexoffice MCP server via HTTP
  • The client is configured with a name and the URL from our Tool Router session
  • getTools() retrieves all available Lexoffice tools that the agent can use
  • We're creating a LangChain agent using the GPT-5 model
9

Set up interactive chat interface

let conversationHistory: any[] = [];

console.log("Chat started! Type 'exit' or 'quit' to end the conversation.\n");
console.log("Ask any Lexoffice related question or task to the agent.\n");

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

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;
    }

    conversationHistory.push({ role: "user", content: trimmedInput });
    console.log("\nAgent is thinking...\n");

    const response = await agent.invoke({ messages: conversationHistory });
    conversationHistory = response.messages;

    const finalResponse = response.messages[response.messages.length - 1]?.content;
    console.log(`Agent: ${finalResponse}\n`);
        
        rl.prompt();
    });

    rl.on('close', () => {
        console.log('\n👋 Session ended.');
        process.exit(0);
    });
What's happening:
  • We initialize an empty conversationHistory list to maintain context across interactions
  • A readline interface is used to continuously accept 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 invoke() method with the full conversation history
  • Users can type 'exit', 'quit', or 'bye' to end the chat session gracefully
10

Run the application

main().catch((err) => {
    console.error('Fatal error:', err);
    process.exit(1);
});
What's happening:
  • We call the main() function to start the application

Complete Code

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

import { Composio } from '@composio/core';
import { LangchainProvider } from '@composio/langchain';
import { MultiServerMCPClient } from "@langchain/mcp-adapters";  
import { createAgent } from "langchain";
import * as readline from 'readline';
import 'dotenv/config';

const composioApiKey = process.env.COMPOSIO_API_KEY;
const userId = process.env.COMPOSIO_USER_ID;

if (!composioApiKey) throw new Error('COMPOSIO_API_KEY is not set');
if (!userId) throw new Error('COMPOSIO_USER_ID is not set');

async function main() {
    const composio = new Composio({
        apiKey: composioApiKey as string,
        provider: new LangchainProvider()
    });

    const session = await composio.create(
        userId as string,
        {
            toolkits: ['lexoffice']
        }
    );

    const url = session.mcp.url;
    
    const client = new MultiServerMCPClient({
        "lexoffice-agent": {
            transport: "http",
            url: url,
            headers: {
                "x-api-key": process.env.COMPOSIO_API_KEY
            }
        }
    });
    
    const tools = await client.getTools();
  
    const agent = createAgent({ model: "gpt-5", tools });
    
    let conversationHistory: any[] = [];
    
    console.log("Chat started! Type 'exit' or 'quit' to end the conversation.\n");
    console.log("Ask any Lexoffice related question or task to the agent.\n");
    
    const rl = readline.createInterface({
        input: process.stdin,
        output: process.stdout,
        prompt: 'You: '
    });

    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;
        }
        
        conversationHistory.push({ role: "user", content: trimmedInput });
        console.log("\nAgent is thinking...\n");
        
        const response = await agent.invoke({ messages: conversationHistory });
        conversationHistory = response.messages;
        
        const finalResponse = response.messages[response.messages.length - 1]?.content;
        console.log(`Agent: ${finalResponse}\n`);
        
        rl.prompt();
    });

    rl.on('close', () => {
        console.log('\nSession ended.');
        process.exit(0);
    });
}

main().catch((err) => {
    console.error('Fatal error:', err);
    process.exit(1);
});

Conclusion

You've successfully built a LangChain agent that can interact with Lexoffice 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.
TOOLS

Supported Tools

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

Create Article

Tool to create a new article (product or service) in Lexoffice.

Create contact

Tool to create a new contact (customer or vendor) in Lexoffice.

Create Credit Note

Tool to create a credit note in Lexoffice.

Create Delivery Note

Create a delivery note in lexoffice.

Create Event Subscription

Tool to register a new webhook for Lexoffice events.

Create Order Confirmation

Tool to create an Order Confirmation in Lexoffice/Lexware.

Create Quotation

Tool to create a quotation in Lexoffice.

Create Voucher

Tool to create a bookkeeping voucher in Lexoffice.

Delete Article

Tool to permanently delete an article by its ID.

Delete Event Subscription

Tool to delete an event subscription by its ID.

Download File

Download a file from lexoffice by its ID.

Get Article

Tool to retrieve an article by ID from Lexoffice.

Get Contact

Tool to retrieve a specific contact by its ID.

Get Credit Note

Tool to retrieve a credit note by its UUID from Lexoffice.

Get Credit Note Document

Tool to render a credit note document (PDF).

Get Delivery Note

Tool to retrieve a specific delivery note from Lexoffice by its ID.

Get Dunning

Tool to retrieve a dunning document by its ID.

Get Dunning Document

Tool to render and retrieve a dunning document (PDF) reference.

Get Event Subscription

Tool to retrieve a specific event subscription by its ID.

Get Invoice

Tool to retrieve a specific invoice by its UUID.

Get Invoice Document

Tool to render an Invoice Document (PDF) by invoice ID.

Get Order Confirmation

Tool to retrieve a specific order confirmation by its ID.

Render Order Confirmation Document

Tool to render an Order Confirmation Document as PDF.

Get Payment Information

Tool to retrieve payment information for a specific voucher (invoice or credit note) from Lexoffice.

Get Profile

Retrieves the user and company profile information from Lexoffice.

Get Quotation

Tool to retrieve a quotation by its ID.

Get Quotation Document

Tool to render a quotation document as a PDF file.

Get Voucher

Tool to retrieve a specific voucher by its UUID.

List Articles

Tool to list articles from Lexoffice using filters and pagination.

List Contacts

Tool to retrieve all contacts from Lexoffice with optional filters.

List Countries

Tool to retrieve the list of all available countries with tax classifications from Lexoffice.

List Event Subscriptions

Tool to retrieve all event subscriptions for the current access token.

List Payment Conditions

Tool to retrieve list of currently configured payment conditions from Lexoffice.

List Posting Categories

Tool to retrieve the list of posting categories for bookkeeping vouchers (revenue or expense) supported in lexoffice.

List Print Layouts

Tool to retrieve all print layouts for invoices and other documents.

List Recurring Templates

Tool to retrieve all recurring templates from Lexoffice.

List Voucherlist

Tool to retrieve voucherlist from Lexoffice including bookkeeping vouchers (salesinvoices, salescreditnotes), invoices, credit notes, order confirmations, quotations, and delivery notes.

List Vouchers

Tool to filter vouchers by voucher number from Lexoffice.

Update Article

Tool to update an existing article in Lexoffice with new data.

Update lexoffice contact

Tool to update an existing contact in lexoffice.

Upload Voucher File

Tool to upload and assign files (PDF or image) to a specific voucher in lexoffice.

FRAMEWORKS

How to build Lexoffice MCP Agent with another framework

OpenAI Agents SDK logo

OpenAI Agents SDK

Use Lexoffice MCP with OpenAI Agents SDK

Claude Agent SDK logo

Claude Agent SDK

Use Lexoffice MCP with Claude Agent SDK

Claude Code logo

Claude Code

Use Lexoffice MCP with Claude Code

Claude Cowork logo

Claude Cowork

Use Lexoffice MCP with Claude Cowork

Codex logo

Codex

Use Lexoffice MCP with Codex

OpenClaw logo

OpenClaw

Use Lexoffice MCP with OpenClaw

Hermes logo

Hermes

Use Lexoffice MCP with Hermes

CLI logo

CLI

Use Lexoffice MCP with CLI

Google ADK logo

Google ADK

Use Lexoffice MCP with Google ADK

Vercel AI SDK logo

Vercel AI SDK

Use Lexoffice MCP with Vercel AI SDK

Mastra AI logo

Mastra AI

Use Lexoffice MCP with Mastra AI

LlamaIndex logo

LlamaIndex

Use Lexoffice MCP with LlamaIndex

CrewAI logo

CrewAI

Use Lexoffice MCP with CrewAI

FAQ

Frequently asked questions

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

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 Lexoffice tools.

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

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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.

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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.

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