Rechnungslotse

Rechnungslotse MCP Server

A hosted Model Context Protocol server for German electronic invoicing: create, validate and read XRechnung and ZUGFeRD files against EN 16931.

Seven of the eighteen tools work without an account or API key. Point your client at the URL below and start.

https://rechnungslotse.de/api/mcp

Transport: Streamable HTTP. Authentication: OAuth 2.1 (only needed for the account tools).

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Why another e-invoicing server

Most e-invoicing MCP servers validate. This one also creates — and it knows the German specifics that a generic EN 16931 validator does not: Leitweg-ID check digits, the mandatory fields of § 14 UStG, the small-business threshold of § 19 UStG, and the staged German mandate (2025 receive, 2027/2028 issue).

Validation runs against the full KoSIT rule set. Every violation comes back with its rule ID and a plain-language explanation, plus a link to a page explaining that rule.

Files are never stored. They exist for the duration of the call.

Setup

Claude Code

claude mcp add --transport http rechnungslotse https://rechnungslotse.de/api/mcp

Claude Desktop, Cursor, VS Code, Zed

Add to your MCP configuration:

{
  "mcpServers": {
    "rechnungslotse": {
      "type": "http",
      "url": "https://rechnungslotse.de/api/mcp"
    }
  }
}

ChatGPT

Add https://rechnungslotse.de/api/mcp as a remote MCP server in the connector settings.

Official MCP Registry

de.rechnungslotse/e-rechnung

Tools

Without an account

No key, no signup, no stored data.

Tool	What it does
rechnung_pruefen	Validate an XRechnung or ZUGFeRD PDF against EN 16931 and the KoSIT rules. Returns every violation with rule ID and plain text.
rechnung_lesen	Read an invoice into structured data: sender, recipient, line items, totals, due date, bank details.
fehler_erklaeren	Explain a rule ID from a rejection message (BR-08, BR-CO-15, PEPPOL-EN16931-R053): what the rule requires, common causes, how to fix it.
pflicht_pruefen	Answer when a specific German business must issue e-invoices, with date and statute (§ 27 Abs. 38 UStG, § 34a UStDV).
pflichtangaben_pruefen	Check an invoice against the mandatory fields of § 14 UStG — also works for a Word or PDF invoice with no data set. Handles small-amount invoices (§ 33 UStDV), small businesses and reverse charge.
leitweg_pruefen	Split a Leitweg-ID into its parts, recompute the MOD 97-10 check digit, find transposed digits.
kleinunternehmer_pruefen	Check both turnover limits of the small-business rule as it stands since 2025: €25,000 previous year, €100,000 current year.

With a connected account

Free plan: three invoices a month. These tools act inside one business and require OAuth.

Tool	What it does
rechnung_erstellen	Create a validated e-invoice (XRechnung, PDF, ZUGFeRD). Idempotent by order number.
rechnung_datei	Fetch a generated invoice in a given format.
rechnungen_suchen	List invoices by state, period or search term, with open amount and overdue flag.
kunden_suchen	Look up a customer's full address from the address book.
betrieb_lesen	Read the business's master data.
leistung_erfassen	Log work done for a customer — hours, material, flat rates, travel.
leistungen_offen	Show what is logged but not yet invoiced.
leistungen_abrechnen	Turn one customer's open items into a validated e-invoice.
zahlung_erfassen	Record an incoming payment against an invoice.
offene_posten	List overdue invoices with days overdue and the dunning level due.
umsatzsteuer_aufstellung	Net and tax totals per rate for a VAT return, with ELSTER field numbers.

Examples

Ask your assistant:

"This XRechnung was rejected with BR-DE-15. What does that mean and how do I fix it?"

"Read this ZUGFeRD PDF and tell me what's on it."

"My turnover was €22,000 last year and €41,000 so far this year. Am I still a small business?"

"From 2028, do I have to issue e-invoices? I sell to businesses, turnover under €800,000."

Authentication

The seven tools above need nothing. tools/list works unauthenticated, so a client sees every tool before connecting.

Calling an account tool without a token returns 401 with a WWW-Authenticate header pointing at the resource metadata. MCP clients turn that into a connect prompt. OAuth 2.1 with PKCE, dynamic client registration and client ID metadata documents are all supported:

• https://rechnungslotse.de/.well-known/oauth-protected-resource
• https://rechnungslotse.de/.well-known/oauth-authorization-server

Limits and honesty

• German invoicing law. The statutes referenced are German. The EN 16931 validation itself is European and applies more widely, but the mandate logic, Leitweg-ID and § 14 UStG checks are specific to Germany.
• Not tax advice. The tools report what the rules say. Edge cases belong with a tax adviser.
• Rate limits apply to the free tools to keep them available.
• No file storage. Uploaded invoices are held in memory for the call and discarded.

Links

• Server and setup: https://rechnungslotse.de/mcp
• Rule database, one page per validation rule: https://rechnungslotse.de/fehler
• Free browser tools (validator, viewer, checkers): https://rechnungslotse.de/tools
• REST API for developers: https://rechnungslotse.de/entwickler

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Deutsch

MCP-Server für die deutsche E-Rechnung. XRechnung und ZUGFeRD erstellen, gegen EN 16931 und die KoSIT-Regeln prüfen und im Klartext lesen — direkt aus Claude, ChatGPT oder einem anderen MCP-Client.

Sieben der achtzehn Werkzeuge laufen ohne Konto und ohne Schlüssel: prüfen, lesen, Prüfregeln erklären, E-Rechnungspflicht klären, Pflichtangaben nach § 14 UStG, Leitweg-ID und die Kleinunternehmergrenze nach § 19 UStG. Dateien werden dabei nicht gespeichert.

Adresse eintragen und loslegen:

https://rechnungslotse.de/api/mcp

Die übrigen elf Werkzeuge arbeiten im verbundenen Betrieb: Rechnung erstellen, Leistungen erfassen und abrechnen, Zahlungen verbuchen, offene Posten, Umsatzsteuer-Aufstellung mit ELSTER-Kennziffern. Drei Rechnungen im Monat sind dauerhaft kostenlos.

Ausführlich: https://rechnungslotse.de/mcp

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Operated by AOS Digital, Germany. This repository documents the hosted server; it is not the product source.