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ZUGFeRD Validator MCP server

Which servers in the official MCP registry are ZUGFeRD Validator's own, whether they answer, and what they offer. A program checked each of these, nobody copied them from a product page.

read 2026-10-26

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Whose server it is
  • Registry namede.zugferd-validator/validatorverified in the MCP registry

The registry name sits under zugferd-validator.de. The registry only lets a publisher use that namespace after proving control of the domain through DNS or HTTP.

When we asked itchecked 2026-10-26
  • Stateanswerschecked 2026-10-26
  • Tools5
  • Server calls itselfzugferd-validator
  • Server version1.0.0
  • Protocol version2025-06-18

On 2026-10-26 the server answered initialize and tools/list without a sign-in. First answer in 647 ms.

Should an agent connect itNot proven either way yet
  • Its tools do check ZUGFeRD and XRechnung files for errors before sending, but not convert PDF, Word or Excel invoices into e-invoices.
  • Checked on 1 of the 7 days it takes to judge reliability.

Once connected

  • For "check ZUGFeRD and XRechnung files for errors before sending", the likely first call is validate_invoice.
  • create_invoice change data without a sign-in: anyone with the address can call them.

Said by rules from the measurements above. The likely first call is a model's pick from the tool list; read its description before relying on it.

Measured dailydaily checks: 1, the first on 2026-10-26
  • INITE MCP scoreafter a weeka score needs 7 daily checks: 1 so far
  • What an agent can do with it1 of 2 use cases
  • Use78 npm downloads a week
  • Answeredmeasuring1 of the 7 daily checks it takes to print a share
  • Median first answer786 ms
  • Space in an agent's context≈ 2,179 tokensthe definitions of all its tools (5), which an agent carries on every turn
  • Tool definitionsB · 83 of 100
  • Typed results0 of 5 toolsdeclared outputSchema: results come typed, read once
  • Not saying whether it only reads or can destroy: 5 of 5

What an agent can do with it

  • can do · check ZUGFeRD and XRechnung files for errors before sending
  • cannot · convert PDF, Word or Excel invoices into e-invoices
  • not sure · save a validation report as proof of checking

Each of the product's use cases, put to Jev against this server's tool list: can an agent do it with these tools?

Worth a look

  • Tools that change data, on a server that answers without a sign-in: create_invoice

A program checks the server once a day: initialize and tools/list, no model. Tokens are the definitions' length at about four characters a token. The grade averages six checks of every tool's name, description, schema and annotations; it says how well the tools are described, not whether they work. The score weighs what was measured and nothing else: answering (30%), doing the product's job (25%), definitions (20%), context (10%) and use (15%). A part that was not measured is left out, and a hidden instruction caps the score at 40. The state of vendors' MCP servers: method and numbers →

Tools it offers5 tools · read 2026-10-26
  • validate_invoice

    Validiert eine E-Rechnung (ZUGFeRD/Factur-X PDF oder XRechnung XML) gegen EN 16931 und gibt strukturierte Ergebnisse mit Korrekturvorschlägen zurück.

  • extract_xml

    Extrahiert die eingebettete XML-Datei aus einem ZUGFeRD/Factur-X PDF.

  • check_consistency

    Prüft ob die sichtbaren PDF-Daten mit den eingebetteten XML-Daten übereinstimmen.

  • create_invoice

    Erstellt aus strukturierten Daten eine valide E-Rechnung — entweder als ZUGFeRD-PDF (PDF/A-3 mit eingebettetem XML) oder als reines XRechnung-XML (mit Leitweg-ID für B2G). Unterstützt mehrere Positionen, alle USt-Kategorien…

  • validation_report

    Erzeugt aus einer E-Rechnung einen Validierungsbericht als PDF (PDF/A-3b) zum Ablegen und Weitergeben. Der Bericht nennt Ergebnis, alle Meldungen mit Regel-ID und Feld, den Prüfzeitpunkt, Format und Profil, die SHA-256-Prüfsumme der…

How to connect

Add the server to your MCP client config. Claude Desktop, Cursor and most other clients read this shape:

{
  "mcpServers": {
    "validator": {
      "type": "http",
      "url": "https://api.zugferd-validator.de/mcp"
    }
  }
}

Add it

Claude Code, in a terminal

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

Add to CursorAdd to VS Code

claude.ai, ChatGPT and other clients: add https://api.zugferd-validator.de/mcp as a custom connector in the settings.

Also shipped through: npm

Each line is something a program found when it went looking: the registry entry, the server's own answer, a spec that parses. A missing line means we did not find it, not that it does not exist.