Verifactu MCP Server

verifactu-mcp

On PyPI as verifactu-keyflint-mcp (the name verifactu-mcp belongs to another project).

MCP server for Spanish invoicing compliance, built for AI agents working for gestorías, accountants and invoicing-software teams. Offline and stateless: nothing is stored and nothing is sent to the AEAT.

• Audit VERI*FACTU chains: recompute the SHA-256 fingerprint (huella) of every record (alta and anulación) exactly as the AEAT specifies, and check that each record links to the previous one. Works on JSON records or on the XML any invoicing program exports (validated against the official SuministroLR.xsd).
• AEAT tax QR: URL and PNG/SVG image (error correction M) for VERI*FACTU and non-VERI*FACTU systems, production or test portal, with the printing rules.
• Facturae 3.2.2: build an invoice from plain data (totals, VAT breakdown, IRPF withholding, recargo de equivalencia, DIR3 codes for FACe, IBAN) and validate any Facturae file: official XSD, the arithmetic FACe checks, NIFs, DIR3 roles and signature presence.

The fingerprint code is tested against the three reference vectors published by the AEAT.

Tools

Unreadable or invalid input is never charged; a tool that fails after charging is refunded.

Install

Claude Desktop / Claude Code / Cursor (mcpServers entry):

{
  "verifactu": {
    "command": "uvx",
    "args": ["--from", "verifactu-keyflint-mcp", "verifactu-mcp"],
    "env": { "KEYFLINT_LICENSE": "LIC-..." }
  }
}

Hosted (one server, many buyers): verifactu-mcp --http or the Dockerfile; each request carries Authorization: Bearer LIC-....

Environment: KEYFLINT_LICENSE, KEYFLINT_URL, KEYFLINT_PUBLIC_KEYS, KEYFLINT_CHECKOUT_URL, VERIFACTU_PRICES (e.g. validate_invoice_chain=5,build_facturae=4), VERIFACTU_MAX_BYTES (default 10 MB).

Visual cards (MCP Apps)

In Claude, ChatGPT, VS Code and Goose every paid tool and credits_balance renders as an interactive card in the chat: credit balance with a refill bar and a buy button, or a result summary (key figures, issues, table preview and credits charged). It is the ui://verifactu/card.html resource, self-contained with no network access. Other clients keep getting the same JSON as before.

Legal status (checked 2026-11-05)

• VERI*FACTU (RD 1007/2023, Orden HAC/1177/2024; dates from RD-ley 15/2025): 1 Jan 2027 for corporate income tax payers, 1 Jul 2027 for everyone else. Hacienda announced on 5 Oct 2026 a further delay to October 2028, not yet published in the BOE. Taxpayers on SII and the foral territories are out of scope.
• Mandatory B2B e-invoicing (RD 238/2026, Orden HAC/1028/2026): 6 Oct 2027 for turnover above 8 M EUR, 6 Oct 2028 for the rest; EN 16931 in UBL, CII, EDIFACT or Facturae.
• Facturae with XAdES signature is mandatory for invoices to public administrations through FACe.

verifactu_calendar returns this with sources. Always confirm in the BOE.

Scope and limits

• Not an invoicing system (SIF): it keeps no records, sends nothing to the AEAT and does not replace the producer's declaración responsable. Use it to check what a SIF produced, or to prepare data.
• build_facturae produces unsigned XML. Sign it (XAdES-EPES) with the issuer's certificate before sending to FACe or a B2B platform. Corrective invoices (InvoiceClass OR) and batches are validated but not built yet.
• If a stored fingerprint only matches after removing trailing zeros from the amounts, it is reported as a warning (correcta_sin_ceros): the record was generated with amounts written differently from the XML.

Sources

• AEAT, Detalle de las especificaciones técnicas para generación de la huella o hash de los registros de facturación (reference vectors in tests/test_core.py).
• AEAT, Características del QR y especificaciones del servicio de cotejo.
• AEAT web service schemas SuministroLR.xsd / SuministroInformacion.xsd, and Facturaev3_2_2.xsd (facturae.gob.es), bundled in src/verifactu_mcp/schemas/ with the W3C xmldsig schema.

Development

pip install -e '.[test]'
pytest -q

Business Source License 1.1. Source available; production use needs a KeyFlint license (or must be non-commercial). Each version becomes Apache 2.0 four years after release. See LICENSE. The bundled XSD files belong to their publishers (AEAT, Ministerio de Hacienda, W3C).