How to integrate Lexoffice MCP with Mastra AI

This guide walks you through connecting Lexoffice to Mastra AI 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 Mastra AI 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 Mastra AI 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 Mastra AI 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

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TL;DR

Here's what you'll learn:
  • Set up your environment so Mastra, OpenAI, and Composio work together
  • Create a Tool Router session in Composio that exposes Lexoffice tools
  • Connect Mastra's MCP client to the Composio generated MCP URL
  • Fetch Lexoffice tool definitions and attach them as a toolset
  • Build a Mastra agent that can reason, call tools, and return structured results
  • Run an interactive CLI where you can chat with your Lexoffice agent

What is Mastra AI?

Mastra AI is a TypeScript framework for building AI agents with tool support. It provides a clean API for creating agents that can use external services through MCP.

Key features include:

  • MCP Client: Built-in support for Model Context Protocol servers
  • Toolsets: Organize tools into logical groups
  • Step Callbacks: Monitor and debug agent execution
  • OpenAI Integration: Works with OpenAI models via @ai-sdk/openai

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 step09 STEPS
1

Prerequisites

Before starting, make sure you have:
  • Node.js 18 or higher
  • A Composio account with an active API key
  • An OpenAI API key
  • Basic familiarity with TypeScript
2

Getting API Keys for OpenAI and Composio

OpenAI API Key
  • Go to the OpenAI dashboard and create an API key.
  • You need credits or a connected billing setup to use the models.
  • Store the key somewhere safe.
Composio API Key
  • Log in to the Composio dashboard.
  • Go to Settings and copy your API key.
  • This key lets your Mastra agent talk to Composio and reach Lexoffice through MCP.
3

Install dependencies

bash
npm install @composio/core @mastra/core @mastra/mcp @ai-sdk/openai dotenv

Install the required packages.

What's happening:

  • @composio/core is the Composio SDK for creating MCP sessions
  • @mastra/core provides the Agent class
  • @mastra/mcp is Mastra's MCP client
  • @ai-sdk/openai is the model wrapper for OpenAI
  • dotenv loads environment variables from .env
4

Set up environment variables

bash
COMPOSIO_API_KEY=your_composio_api_key_here
COMPOSIO_USER_ID=your_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
  • COMPOSIO_USER_ID tells Composio which user this session belongs to
  • OPENAI_API_KEY lets the Mastra agent call OpenAI models
5

Import libraries and validate environment

typescript
import "dotenv/config";
import { openai } from "@ai-sdk/openai";
import { Agent } from "@mastra/core/agent";
import { MCPClient } from "@mastra/mcp";
import { Composio } from "@composio/core";
import * as readline from "readline";

import type { AiMessageType } from "@mastra/core/agent";

const openaiAPIKey = process.env.OPENAI_API_KEY;
const composioAPIKey = process.env.COMPOSIO_API_KEY;
const composioUserID = process.env.COMPOSIO_USER_ID;

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

const composio = new Composio({
  apiKey: composioAPIKey as string,
});
What's happening:
  • dotenv/config auto loads your .env so process.env.* is available
  • openai gives you a Mastra compatible model wrapper
  • Agent is the Mastra agent that will call tools and produce answers
  • MCPClient connects Mastra to your Composio MCP server
  • Composio is used to create a Tool Router session
6

Create a Tool Router session for Lexoffice

typescript
async function main() {
  const session = await composio.create(
    composioUserID as string,
    {
      toolkits: ["lexoffice"],
    },
  );

  const composioMCPUrl = session.mcp.url;
  console.log("Lexoffice MCP URL:", composioMCPUrl);
What's happening:
  • create spins up a short-lived MCP HTTP endpoint for this user
  • The toolkits array contains "lexoffice" for Lexoffice access
  • session.mcp.url is the MCP URL that Mastra's MCPClient will connect to
7

Configure Mastra MCP client and fetch tools

typescript
const mcpClient = new MCPClient({
    id: composioUserID as string,
    servers: {
      nasdaq: {
        url: new URL(composioMCPUrl),
        requestInit: {
          headers: session.mcp.headers,
        },
      },
    },
    timeout: 30_000,
  });

console.log("Fetching MCP tools from Composio...");
const composioTools = await mcpClient.getTools();
console.log("Number of tools:", Object.keys(composioTools).length);
What's happening:
  • MCPClient takes an id for this client and a list of MCP servers
  • The headers property includes the x-api-key for authentication
  • getTools fetches the tool definitions exposed by the Lexoffice toolkit
8

Create the Mastra agent

typescript
const agent = new Agent({
    name: "lexoffice-mastra-agent",
    instructions: "You are an AI agent with Lexoffice tools via Composio.",
    model: "openai/gpt-5",
  });
What's happening:
  • Agent is the core Mastra agent
  • name is just an identifier for logging and debugging
  • instructions guide the agent to use tools instead of only answering in natural language
  • model uses openai("gpt-5") to configure the underlying LLM
9

Set up interactive chat interface

typescript
let messages: AiMessageType[] = [];

console.log("Chat started! Type 'exit' or 'quit' to end.\n");

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

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;
  }

  messages.push({
    id: crypto.randomUUID(),
    role: "user",
    content: trimmedInput,
  });

  console.log("\nAgent is thinking...\n");

  try {
    const response = await agent.generate(messages, {
      toolsets: {
        lexoffice: composioTools,
      },
      maxSteps: 8,
    });

    const { text } = response;

    if (text && text.trim().length > 0) {
      console.log(`Agent: ${text}\n`);
        messages.push({
          id: crypto.randomUUID(),
          role: "assistant",
          content: text,
        });
      }
    } catch (error) {
      console.error("\nError:", error);
    }

    rl.prompt();
  });

  rl.on("close", async () => {
    console.log("\nSession ended.");
    await mcpClient.disconnect();
    process.exit(0);
  });
}

main().catch((err) => {
  console.error("Fatal error:", err);
  process.exit(1);
});
What's happening:
  • messages keeps the full conversation history in Mastra's expected format
  • agent.generate runs the agent with conversation history and Lexoffice toolsets
  • maxSteps limits how many tool calls the agent can take in a single run
  • onStepFinish is a hook that prints intermediate steps for debugging

Complete Code

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

typescript
import "dotenv/config";
import { openai } from "@ai-sdk/openai";
import { Agent } from "@mastra/core/agent";
import { MCPClient } from "@mastra/mcp";
import { Composio } from "@composio/core";
import * as readline from "readline";

import type { AiMessageType } from "@mastra/core/agent";

const openaiAPIKey = process.env.OPENAI_API_KEY;
const composioAPIKey = process.env.COMPOSIO_API_KEY;
const composioUserID = process.env.COMPOSIO_USER_ID;

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

const composio = new Composio({ apiKey: composioAPIKey as string });

async function main() {
  const session = await composio.create(composioUserID as string, {
    toolkits: ["lexoffice"],
  });

  const composioMCPUrl = session.mcp.url;

  const mcpClient = new MCPClient({
    id: composioUserID as string,
    servers: {
      lexoffice: {
        url: new URL(composioMCPUrl),
        requestInit: {
          headers: session.mcp.headers,
        },
      },
    },
    timeout: 30_000,
  });

  const composioTools = await mcpClient.getTools();

  const agent = new Agent({
    name: "lexoffice-mastra-agent",
    instructions: "You are an AI agent with Lexoffice tools via Composio.",
    model: "openai/gpt-5",
  });

  let messages: AiMessageType[] = [];

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

  rl.prompt();

  rl.on("line", async (input: string) => {
    const trimmed = input.trim();
    if (["exit", "quit"].includes(trimmed.toLowerCase())) {
      rl.close();
      return;
    }

    messages.push({ id: crypto.randomUUID(), role: "user", content: trimmed });

    const { text } = await agent.generate(messages, {
      toolsets: { lexoffice: composioTools },
      maxSteps: 8,
    });

    if (text) {
      console.log(`Agent: ${text}\n`);
      messages.push({ id: crypto.randomUUID(), role: "assistant", content: text });
    }

    rl.prompt();
  });

  rl.on("close", async () => {
    await mcpClient.disconnect();
    process.exit(0);
  });
}

main();

Conclusion

You've built a Mastra AI agent that can interact with Lexoffice through Composio's Tool Router. You can extend this further by:
  • Adding other toolkits like Gmail, Slack, or GitHub
  • Building a web-based chat interface around this agent
  • Using multiple MCP endpoints to enable cross-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

LangChain logo

LangChain

Use Lexoffice MCP with LangChain

Vercel AI SDK logo

Vercel AI SDK

Use Lexoffice MCP with Vercel AI SDK

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. Mastra 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 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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