Validates European e-invoices (ZUGFeRD, Factur-X, XRechnung) against the EN 16931 standard and returns structured JSON with actual fix suggestions. You get three tools: validate_invoice checks compliance and returns errors with XPath references and concrete XML examples, extract_xml pulls embedded XML from ZUGFeRD PDFs, and check_consistency catches manipulation by comparing visible PDF data against the embedded invoice data. Each error includes a rule ID, affected field, and actionable correction. Hosted in Germany using Mustang Project and KoSIT engines, so no local validation infrastructure needed. Useful if you're building invoicing systems, financial automation, or need to verify supplier invoices in AI workflows without parsing spec documents yourself.