How to integrate Lexoffice MCP with LlamaIndex

This guide walks you through connecting Lexoffice to LlamaIndex 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 LlamaIndex 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.

Lexoffice logoLexoffice
Api Key

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 LlamaIndex 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 LlamaIndex 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

TL;DR

Here's what you'll learn:
  • Set your OpenAI and Composio API keys
  • Install LlamaIndex and Composio packages
  • Create a Composio Tool Router session for Lexoffice
  • Connect LlamaIndex to the Lexoffice MCP server
  • Build a Lexoffice-powered agent using LlamaIndex
  • Interact with Lexoffice through natural language

What is LlamaIndex?

LlamaIndex is a data framework for building LLM applications. It provides tools for connecting LLMs to external data sources and services through agents and tools.

Key features include:

  • ReAct Agent: Reasoning and acting pattern for tool-using agents
  • MCP Tools: Native support for Model Context Protocol
  • Context Management: Maintain conversation context across interactions
  • Async Support: Built for async/await patterns

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 you begin, make sure you have:
  • Python 3.8/Node 16 or higher installed
  • A Composio account with the API key
  • An OpenAI API key
  • A Lexoffice account and project
  • Basic familiarity with async Python/Typescript
2

Getting API Keys for OpenAI, Composio, and Lexoffice

OpenAI API key (OPENAI_API_KEY)
  • Go to the OpenAI dashboard
  • Create an API key if you don't have one
  • Assign it to OPENAI_API_KEY in .env
Composio API key and user ID
  • Log into the Composio dashboard
  • Copy your API key from Settings
    • Use this as COMPOSIO_API_KEY
  • Pick a stable user identifier (email or ID)
    • Use this as COMPOSIO_USER_ID
3

Installing dependencies

npm install @composio/llamaindex @llamaindex/openai @llamaindex/tools @llamaindex/workflow dotenv

Create a new Typescript project and install the necessary dependencies:

  • @composio/llamaindex: Composio's LlamaIndex integration
  • @llamaindex/openai: OpenAI LLM integration
  • @llamaindex/tools: MCP client for LlamaIndex
  • @llamaindex/workflow: Workflow framework for LlamaIndex
  • dotenv: Environment variable management
4

Set environment variables

bash
OPENAI_API_KEY=your-openai-api-key
COMPOSIO_API_KEY=your-composio-api-key
COMPOSIO_USER_ID=your-user-id

Create a .env file in your project root:

These credentials will be used to:

  • Authenticate with OpenAI's GPT-5 model
  • Connect to Composio's Tool Router
  • Identify your Composio user session for Lexoffice access
5

Import modules

import "dotenv/config";
import readline from "node:readline/promises";
import { stdin as input, stdout as output } from "node:process";

import { Composio } from "@composio/core";

import { mcp } from "@llamaindex/tools";
import { agent as createAgent } from "@llamaindex/workflow";
import { openai } from "@llamaindex/openai";

dotenv.config();

Create a new file called lexoffice_llamaindex_agent.ts and import the required modules:

Key imports:

  • dotenv.config loads .env at runtime
  • readline gives us a simple CLI chat loop
  • Composio is the main Composio SDK client
  • mcp connects to an MCP endpoint
  • createAgent builds a LlamaIndex agent
  • openai configures the LLM backend
6

Load environment variables and initialize Composio

const OPENAI_API_KEY = process.env.OPENAI_API_KEY;
const COMPOSIO_API_KEY = process.env.COMPOSIO_API_KEY;
const COMPOSIO_USER_ID = process.env.COMPOSIO_USER_ID;

if (!OPENAI_API_KEY) throw new Error("OPENAI_API_KEY is not set");
if (!COMPOSIO_API_KEY) throw new Error("COMPOSIO_API_KEY is not set");
if (!COMPOSIO_USER_ID) throw new Error("COMPOSIO_USER_ID is not set");

What's happening:

This ensures missing credentials cause early, clear errors before the agent attempts to initialise.

7

Create a Tool Router session and build the agent function

async function buildAgent() {

  console.log(`Initializing Composio client...${COMPOSIO_USER_ID!}...`);
  console.log(`COMPOSIO_USER_ID: ${COMPOSIO_USER_ID!}...`);

  const composio = new Composio({
    apiKey: COMPOSIO_API_KEY,
    provider: new LlamaindexProvider(),
  });

  const session = await composio.create(
    COMPOSIO_USER_ID!,
    {
      toolkits: ["lexoffice"],
    },
  );

  const mcpUrl = session.mcp.url;
  console.log(`Composio Tool Router MCP URL: ${mcpUrl}`);

  const server = mcp({
    url: mcpUrl,
    clientName: "composio_tool_router_with_llamaindex",
    requestInit: {
      headers: {
        "x-api-key": COMPOSIO_API_KEY!,
      },
    },
    // verbose: true,
  });

  const tools = await server.tools();

  const llm = openai({ apiKey: OPENAI_API_KEY, model: "gpt-5" });

  const agent = createAgent({
    name: "composio_tool_router_with_llamaindex",
        description : "An agent that uses Composio Tool Router MCP tools to perform actions.",
    systemPrompt:
      "You are a helpful assistant connected to Composio Tool Router."+
"Use the available tools to answer user queries and perform Lexoffice actions." ,
    llm,
    tools,
  });

  return agent;
}

What's happening here:

  • We create a Composio client using your API key and configure it with the LlamaIndex provider
  • We then create a tool router MCP session for your user, specifying the toolkits we want to use (in this case, lexoffice)
  • The session returns an MCP HTTP endpoint URL that acts as a gateway to all your configured tools
  • LlamaIndex will connect to this endpoint to dynamically discover and use the available Lexoffice tools.
  • The MCP tools are mapped to LlamaIndex-compatible tools and plug them into the Agent.
8

Create an interactive chat loop

async function chatLoop(agent: ReturnType<typeof createAgent>) {
  const rl = readline.createInterface({ input, output });

  console.log("Type 'quit' or 'exit' to stop.");

  while (true) {
    let userInput: string;

    try {
      userInput = (await rl.question("\nYou: ")).trim();
    } catch {
      console.log("\nAgent: Bye!");
      break;
    }

    if (!userInput) {
      continue;
    }

    const lower = userInput.toLowerCase();
    if (lower === "quit" || lower === "exit") {
      console.log("Agent: Bye!");
      break;
    }

    try {
      process.stdout.write("Agent: ");

      const stream = agent.runStream(userInput);
      let finalResult: any = null;

      for await (const event of stream) {
        // The event.data contains the streamed content
        const data: any = event.data;

        // Check for streaming delta content
        if (data?.delta) {
          process.stdout.write(data.delta);
        }

        // Store final result for fallback
        if (data?.result || data?.message) {
          finalResult = data;
        }
      }

      // If no streaming happened, show the final result
      if (finalResult) {
        const answer =
          finalResult.result ??
          finalResult.message?.content ??
          finalResult.message ??
          "";
        if (answer && typeof answer === "string" && !answer.includes("[object")) {
          process.stdout.write(answer);
        }
      }

      console.log(); // New line after streaming completes
    } catch (err: any) {
      console.error("\nAgent error:", err?.message ?? err);
    }
  }

  rl.close();
}

What's happening:

  • We're creating a direct terminal interface to chat with Lexoffice
  • The LLM's responses are streamed to the CLI for faster interaction.
  • The agent uses context to maintain conversation history
  • The agent processes the request, selects appropriate Lexoffice tools, and returns a result
  • We extract the answer from the result data structure and display it to the user
  • You can type 'quit' or 'exit' to stop the chat loop gracefully
  • Agent responses and any errors are streamed in a clear, readable format
9

Define the main entry point

async function main() {
  try {
    const agent = await buildAgent();
    await chatLoop(agent);
  } catch (err) {
    console.error("Failed to start agent:", err);
    process.exit(1);
  }
}

main();

What's happening here:

  • We're orchestrating the entire application flow
  • The agent gets built with proper error handling
  • Then we kick off the interactive chat loop so you can start talking to Lexoffice
10

Run the agent

npx ts-node llamaindex-agent.ts

When prompted, authenticate and authorise your agent with Lexoffice, then start asking questions.

Complete Code

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

import "dotenv/config";
import readline from "node:readline/promises";
import { stdin as input, stdout as output } from "node:process";

import { Composio } from "@composio/core";
import { LlamaindexProvider } from "@composio/llamaindex";

import { mcp } from "@llamaindex/tools";
import { agent as createAgent } from "@llamaindex/workflow";
import { openai } from "@llamaindex/openai";

dotenv.config();

const OPENAI_API_KEY = process.env.OPENAI_API_KEY;
const COMPOSIO_API_KEY = process.env.COMPOSIO_API_KEY;
const COMPOSIO_USER_ID = process.env.COMPOSIO_USER_ID;

if (!OPENAI_API_KEY) {
    throw new Error("OPENAI_API_KEY is not set in the environment");
  }
if (!COMPOSIO_API_KEY) {
    throw new Error("COMPOSIO_API_KEY is not set in the environment");
  }
if (!COMPOSIO_USER_ID) {
    throw new Error("COMPOSIO_USER_ID is not set in the environment");
  }

async function buildAgent() {

  console.log(`Initializing Composio client...${COMPOSIO_USER_ID!}...`);
  console.log(`COMPOSIO_USER_ID: ${COMPOSIO_USER_ID!}...`);

  const composio = new Composio({
    apiKey: COMPOSIO_API_KEY,
    provider: new LlamaindexProvider(),
  });

  const session = await composio.create(
    COMPOSIO_USER_ID!,
    {
      toolkits: ["lexoffice"],
    },
  );

  const mcpUrl = session.mcp.url;
  console.log(`Composio Tool Router MCP URL: ${mcpUrl}`);

  const server = mcp({
    url: mcpUrl,
    clientName: "composio_tool_router_with_llamaindex",
    requestInit: {
      headers: {
        "x-api-key": COMPOSIO_API_KEY!,
      },
    },
    // verbose: true,
  });

  const tools = await server.tools();

  const llm = openai({ apiKey: OPENAI_API_KEY, model: "gpt-5" });

  const agent = createAgent({
    name: "composio_tool_router_with_llamaindex",
    description:
      "An agent that uses Composio Tool Router MCP tools to perform actions.",
    systemPrompt:
      "You are a helpful assistant connected to Composio Tool Router."+
"Use the available tools to answer user queries and perform Lexoffice actions." ,
    llm,
    tools,
  });

  return agent;
}

async function chatLoop(agent: ReturnType<typeof createAgent>) {
  const rl = readline.createInterface({ input, output });

  console.log("Type 'quit' or 'exit' to stop.");

  while (true) {
    let userInput: string;

    try {
      userInput = (await rl.question("\nYou: ")).trim();
    } catch {
      console.log("\nAgent: Bye!");
      break;
    }

    if (!userInput) {
      continue;
    }

    const lower = userInput.toLowerCase();
    if (lower === "quit" || lower === "exit") {
      console.log("Agent: Bye!");
      break;
    }

    try {
      process.stdout.write("Agent: ");

      const stream = agent.runStream(userInput);
      let finalResult: any = null;

      for await (const event of stream) {
        // The event.data contains the streamed content
        const data: any = event.data;

        // Check for streaming delta content
        if (data?.delta) {
          process.stdout.write(data.delta);
        }

        // Store final result for fallback
        if (data?.result || data?.message) {
          finalResult = data;
        }
      }

      // If no streaming happened, show the final result
      if (finalResult) {
        const answer =
          finalResult.result ??
          finalResult.message?.content ??
          finalResult.message ??
          "";
        if (answer && typeof answer === "string" && !answer.includes("[object")) {
          process.stdout.write(answer);
        }
      }

      console.log(); // New line after streaming completes
    } catch (err: any) {
      console.error("\nAgent error:", err?.message ?? err);
    }
  }

  rl.close();
}

async function main() {
  try {
    const agent = await buildAgent();
    await chatLoop(agent);
  } catch (err: any) {
    console.error("Failed to start agent:", err?.message ?? err);
    process.exit(1);
  }
}

main();

Conclusion

You've successfully connected Lexoffice to LlamaIndex through Composio's Tool Router MCP layer. Key takeaways:
  • Tool Router dynamically exposes Lexoffice tools through an MCP endpoint
  • LlamaIndex's ReActAgent handles reasoning and orchestration; Composio handles integrations
  • The agent becomes more capable without increasing prompt size
  • Async Python provides clean, efficient execution of agent workflows
You can easily extend this to other toolkits like Gmail, Notion, Stripe, GitHub, and more by adding them to the toolkits parameter.
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.

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. LlamaIndex 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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