Lexware Office MCP Server

An MCP server for Lexware Office (formerly Lexoffice). It lets MCP-capable assistants query and manage contacts, sales documents, vouchers, files, payments, webhooks, and reference data through the Lexware Office public API.

The server uses Code Mode: instead of one MCP tool per API endpoint, it exposes two tools — `search` to explore a curated Lexware API catalog and `execute` to run constrained, sandboxed API workflows. This keeps the tool surface small while covering the whole API, including pagination, aggregation, and multi-step reporting in a single call.

> Upgrading from 1.x? The legacy tool-per-endpoint server was removed in 2.0.0. See docs/guide.md#migrating-from-1x.

Features

• Broad Lexware Office API coverage for read and write workflows
• Sales documents: invoices, quotations, order confirmations, credit notes, delivery notes, dunning notices, and down-payment invoices
• Contact management: create, read, and update customers and vendors
• Bookkeeping: vouchers, posting categories, payments, and file uploads
• Reference data: profile, countries, print layouts, payment conditions, recurring templates
• Webhooks: create, list, inspect, and delete event subscriptions
• Read-only by default: writes require explicit opt-in via environment variable

How it works

The server exposes two MCP tools:

• `search` — runs a sandboxed JavaScript async arrow function against a curated OpenAPI-lite Lexware catalog.
• `execute` — runs a sandboxed JavaScript async arrow function with one host capability, `lexware.request`, for relative `/v1/...` Lexware API calls.

Example `execute` call:

async () => {
  const response = await lexware.request({
    method: 'GET',
    path: '/v1/contacts',
    query: { name: 'Muster', page: 0, size: 10 }
  });

  return response.data;
}

The sandbox does not receive the Lexware API key, Node globals, filesystem access, imports, `fetch`, or arbitrary network access. `lexware.request` only accepts relative `/v1/...` paths and sends the API key from the host process.

Binary-safe file uploads

Uploads are binary-safe via `multipart` parts with `contentPath` (host reads a local file from disk), `contentBase64` (binary FormData parts), or `bodyBase64` (raw binary body). The host reads/decodes and builds `Buffer` / `Blob` bodies outside the QuickJS sandbox.

Preferred: `contentPath` — pass the file's absolute path instead of inlining bytes. Requires `LEXWARE_OFFICE_ALLOW_WRITES=true` (uploads are writes) and works only when the MCP server runs on the machine that has the file:

async () => {
  const response = await lexware.request({
    method: 'POST',
    path: '/v1/files',
    multipart: [
      { name: 'file', contentType: 'application/pdf', contentPath: '/absolute/path/to/receipt.pdf' },
      { name: 'type', value: 'voucher' },
    ],
  });
  // response.sent echoes { bytes, parts: [{ name, filename, bytes, sha256 }] } for integrity checks
  return { id: response.data?.id, sent: response.sent };
}

See docs/guide.md for details and all supported modes.

Configuration

Get a Lexware Office API key

Create an API key at .

Prerequisites

• Node.js 22 or higher
• `LEXWARE_OFFICE_API_KEY` environment variable

Claude Desktop / MCP config with NPX

Recommended: consume the packaged server

Run the packaged binary from the latest GitHub release (`#semver:^2` resolves to the newest `v2.x` tag and picks up future releases automatically). The package builds itself during GitHub installs via `prepare`, so users do not need to clone the repository or commit `build/` artifacts.

{
  "mcpServers": {
    "lexware-office": {
      "command": "npx",
      "args": ["-y", "--package=github:JannikWempe/mcp-lexware-office#semver:^2", "lexware-office"],
      "env": {
        "LEXWARE_OFFICE_API_KEY": "YOUR_API_KEY_HERE",
        "LEXWARE_OFFICE_READ_ONLY": "true"
      }
    }
  }
}

Troubleshooting: If the `npx` command above fails during git-dependency preparation with an error mentioning `--before`, your npm user config may contain `minimum-release-age`, which conflicts with npm's internal `--before` flag. Two fixes:

# Option 1: bypass your user config for this invocation
NPM_CONFIG_USERCONFIG=/dev/null \
  npx -y --package=github:JannikWempe/mcp-lexware-office#semver:^2 lexware-office

# Option 2: remove the conflicting setting permanently
npm config delete minimum-release-age --location=user

When this package is published to npm, replace the GitHub package spec with the npm package name:

"args": ["-y", "--package=mcp-lexware-office", "lexware-office"]

Local development from TypeScript source

For local development, you can run the TypeScript source directly with `tsx` after cloning the repo and installing dependencies:

{
  "mcpServers": {
    "lexware-office-local": {
      "command": "npx",
      "args": ["-y", "tsx", "/absolute/path/to/mcp-lexware-office/src/index.ts"],
      "env": {
        "LEXWARE_OFFICE_API_KEY": "YOUR_API_KEY_HERE",
        "LEXWARE_OFFICE_READ_ONLY": "true"
      }
    }
  }
}

Use this source-based setup only for development. End users should prefer the packaged binary above.

Write safety

The server is read-only by default. `POST`, `PUT`, `PATCH`, and `DELETE` requests are blocked unless you explicitly opt in:

{
  "LEXWARE_OFFICE_ALLOW_WRITES": "true"
}

`LEXWARE_OFFICE_READ_ONLY=true` is a hard block that wins over `ALLOW_WRITES=true`:

{
  "LEXWARE_OFFICE_READ_ONLY": "true"
}

See docs/guide.md#permissions for the detailed permission model.

Docker

Build the image:

docker build -t mcp-lexware-office:latest -f src/Dockerfile .

Run it:

docker run -i --rm \
  -e LEXWARE_OFFICE_API_KEY \
  -e LEXWARE_OFFICE_READ_ONLY=true \
  mcp-lexware-office:latest

Build and test

npm run build
npm test

Documentation

• Guide and migration notes
• Lexware Office API key setup

License

MIT. See LICENSE.