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Lexware Office MCP Server

Lexware Office MCP Server

by bdiaby1

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

Related MCP server: lexware-mcp-server

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 https://app.lexoffice.de/addons/public-api.

Prerequisites

  • Node.js 22 or higher

  • LEXWARE_OFFICE_API_KEY environment variable

Claude Desktop / MCP config with NPX

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

License

MIT. See LICENSE.

Available Tools

2 tools
executeA

Execute a constrained Lexware Office API workflow by running a JavaScript async arrow function.

Use search first when you need endpoint/domain guidance; do not guess Lexware paths from memory. The sandbox exposes no API key, filesystem, process, imports, fetch, or arbitrary network access.

Available globals:

declare const spec: LexwareApiCatalog; declare const lexware: { request<T = unknown>(input: LexwareRequest): Promise<LexwareResponse>; json(input: LexwareRequest): Promise; paginate<T = unknown>(input: LexwareRequest, options?: { maxPages?: number }): Promise<T[]>; requireNumber(row: unknown, fieldPath: string): number; requireMoney(row: unknown, fieldPath: string): number; sumMoney(rows: unknown[], fieldPath: string): number; formatMoney(cents: number, currency?: string): string; };

type LexwareRequest = { method?: 'GET' | 'POST' | 'PUT' | 'PATCH' | 'DELETE'; path: string; // relative /v1/... only; no absolute URLs or // hosts query?: Record<string, string | number | boolean | Array<string | number | boolean> | null | undefined>; body?: unknown; // JSON by default; string when rawBody=true (UTF-8 encoded, NOT binary-safe) bodyBase64?: string; // raw binary body as base64; the host decodes it outside the sandbox multipart?: MultipartPart[]; // multipart/form-data uploads (e.g. POST /v1/files); host builds FormData contentType?: string; rawBody?: boolean; accept?: string; }; // At most one of body, bodyBase64, or multipart per request.

type MultipartPart = { name: string; value?: string; // plain text form field contentBase64?: string; // binary part content as base64; host decodes it contentPath?: string; // absolute file path on the MCP server machine; host reads the file directly — preferred for local files (no base64, no size blowup) filename?: string; // defaults to the contentPath basename contentType?: string; }; // Exactly one of value, contentBase64, or contentPath per part.

type LexwareResponse<T = unknown> = { ok: boolean; status: number; statusText: string; data?: T; text?: string; truncated?: boolean; contentType: string; headers: Record<string, string>; errorCategory?: string; retryAfterSeconds?: number; operation?: { operationId: string; method: string; pathTemplate: string; summary: string }; request: { method: string; path: string; query: Record<string, string[]> }; sent?: { bytes: number; sha256?: string; parts?: Array<{ name: string; filename?: string; bytes: number; sha256: string }> }; // echo of uploaded binary payloads for integrity checks };

lexware.request returns all HTTP responses, including non-OK, as LexwareResponse. Check response.ok/status for recovery logic, or use lexware.json(...) / lexware.paginate(...) when you want non-OK or non-JSON responses to throw.

This server is read-only by default. POST, PUT, PATCH, and DELETE are blocked unless the server is started with LEXWARE_OFFICE_ALLOW_WRITES=true. Setting LEXWARE_OFFICE_READ_ONLY=true is a hard block that overrides ALLOW_WRITES. Check spec.info.writesEnabled to branch before attempting a write.

Example:

async () => { const response = await lexware.request({ path: '/v1/contacts', query: { page: 0, size: 5 } }); return { status: response.status, request: response.request, data: response.data }; }

File upload example (bookkeeping Beleg). Never inline file bytes in code — pass the file's absolute path via contentPath and the host reads it from disk:

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' }, ], }); return { status: response.status, id: response.data?.id, sent: response.sent }; }

Inputs: code (required), maxRequests.

Tool Schema Changelog

Recent tool additions, removals, and schema changes observed during successful MCP inspections.

Loading tool schema changelog…

    TDQS

    A4.9/5.0

    Scored across 2 tools

    Disambiguation5/5

    The two tools have clearly distinct purposes: search is for discovering API endpoints and workflows, while execute is for making actual API requests. The descriptions explicitly state to use search before execute, eliminating ambiguity.

    Naming Consistency5/5

    Both tool names are single lowercase verbs ('search' and 'execute'), following a consistent imperative style. There is no mixing of conventions or confusing patterns.

    Tool Count3/5

    With only 2 tools, the server is at the low end of what might be considered adequate. However, the design intentionally uses a minimal pair of discovery and execution, which is reasonable for the broad API access it provides.

    Completeness5/5

    The search tool exposes the full API catalog, including workflows and domain guides, while execute can perform any documented API operation. Together they cover the complete lifecycle of discovering and interacting with the Lexware Office API, leaving no functional gaps.

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