An offline, stateless MCP server for Spanish invoicing compliance: audit VERI*FACTU chains, generate AEAT QR codes, build/validate Facturae 3.2.2 invoices, and run free helper checks.
Audit JSON VERI*FACTU record chains: recompute SHA-256 huella, verify links, PrimerRegistro, duplicates, cancellations, timestamps, and NIF/date/amount/TipoFactura formats (up to 20,000 records; batch continuation via continues_from).
Audit exported VERI*FACTU XML, including RegFactuSistemaFacturacion and SOAP envelopes, with official XSD validation plus all chain/fingerprint checks.
Compute the fingerprint of a single alta or anulación record and return the exact hashed string.
Generate AEAT tax QR URLs and PNG/SVG images for VERIFACTU and non-VERIFACTU systems, in production or test, with printing rules.
Build unsigned Facturae 3.2.2 XML from plain invoice data, including VAT breakdown, IRPF withholding, recargo de equivalencia, DIR3/FACe codes, and IBAN, with XSD validation.
Validate Facturae files: official XSD, FACe arithmetic checks, NIFs, DIR3 roles, and signature presence.
Use free helpers: check QR URLs, validate Spanish NIF/NIE/CIF, get VERI*FACTU/B2B e-invoicing deadlines, view pricing, and check credit balance.
Render interactive result/credit cards in supported MCP Apps clients such as Claude, ChatGPT, VS Code, and Goose.
Click on "Deploy Server".
Wait a few minutes for the server to deploy. Once ready, it will show a "Started" state.
In the chat, type @ followed by the MCP server name and your instructions, e.g., "@verifactu-mcp verify the fingerprints and links in these VERI*FACTU invoice records"
That's it! The server will respond to your query, and you can continue using it as needed.
Here is a step-by-step guide with screenshots.
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.
Tool | Credits | What it does |
| 3 | Audit a chain of records (JSON, up to 20,000): fingerprints, links, PrimerRegistro, duplicates, cancellations of unknown invoices, timestamps, NIF/date/amount/TipoFactura formats. |
| 3 | Same audit on exported XML ( |
| 1 | Fingerprint of one record, with the exact string hashed. |
| 1 | Tax QR URL + image + printing rules. |
| 3 | Facturae 3.2.2 XML (unsigned) from plain invoice data, XSD-validated. |
| 2 | XSD + arithmetic + NIF + DIR3 + signature check of a Facturae file. |
| free | Deadlines in force and what is pending in the BOE, with sources. |
| free | Helpers. |
Unreadable or invalid input is never charged; a tool that fails after charging is refunded.
Related MCP server: BeeL MCP server
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).
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.
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.
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.
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.
pip install -e '.[test]'
pytest -qBusiness 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).
Build a Facturae 3.2.2 invoice (XML) from plain data, with totals computed and the official XSD checked.
invoice:
number (max 20), series, issue_date, operation_date?, currency (EUR), description?, notes?,
legal_literals? [text], receiver_contract_reference?,
seller / buyer: nif, name (company name, or first name with first_surname/second_surname for a person),
address, post_code, town, province, country (ISO alfa-3, default ESP), residence? (R/U/E), email?, phone?;
buyer.face: {oficina_contable, organo_gestor, unidad_tramitadora, organo_proponente?} DIR3 codes for
public administration invoices (FACe), or administrative_centres: [{code, role 01-04, name?}],
lines: [{description, quantity, unit_price, tax_rate (21, 10, 4, 0...), discount_pct?, surcharge_rate?
(recargo de equivalencia 5.2, 1.4, 0.5), tax_type? (01 IVA, 03 IGIC, 02 IPSI), unit? (01 unidades),
receiver_reference?, file_reference?, article_code?}],
withholding?: {rate} (IRPF retention, e.g. 15 or 7), payment?: {due_date, method (transferencia,
domiciliacion, efectivo, tarjeta...), iban, bic?}.
Amounts accept "1.234,56" or "1234.56". Returns xml (UTF-8, unsigned), xml_base64, totals and the
validation report. Invalid data is refused before charging. Sign the XML (XAdES) before sending to FACe.
Inputs: invoice (required). Returns: object
Check a tax QR URL read from an invoice: official AEAT host, path, parameters and formats. Free.
Inputs: url (required). Returns: object
Remaining credits on your KeyFlint license. Free.
Inputs: no named parameters. Returns: object
Generate the AEAT tax QR ("QR tributario") of an invoice: URL and image.
Args:
nif: Issuer NIF. numserie: Invoice series + number exactly as registered.
fecha: Issue date (DD-MM-AAAA; AAAA-MM-DD and DD/MM/AAAA are converted).
importe: ImporteTotal with decimal point, e.g. "241.40".
verifactu: true for VERI*FACTU systems (ValidarQR), false for non-verifiable systems (ValidarQRNoVerifactu).
environment: produccion (default) or pruebas (AEAT test portal).
size_px: Image width in pixels (100-2000). image_format: png (default) or svg.
The image uses error correction level M. print_rules says how it must appear on the invoice.
Inputs: nif (required), fecha (required), importe (required), numserie (required), +4 more. Returns: object
Credit price of each tool and where to buy credits. Free.
Inputs: no named parameters. Returns: object
Validate a Facturae 3.2.2 file (.xml or signed .xsig) before sending it to FACe or a client.
Checks the official XSD, the arithmetic FACe checks (line amounts, tax quotas, header vs line bases, totals, batch totals, installments), NIFs of resident parties, the three DIR3 codes for public administrations, and whether the file is signed. Files that are not Facturae are not charged.
Inputs: content, content_base64. Returns: object
Audit a VERI*FACTU chain of records (in generation order) given as JSON objects.
Each record has the fields of verifactu_hash plus Huella (stored fingerprint) and optionally
HuellaAnterior or RegistroAnterior {IDEmisorFactura, NumSerieFactura, FechaExpedicionFactura, Huella} and
PrimerRegistro ("S"). For every record the fingerprint is recomputed and compared, and the link to the
previous record checked. Reports chain breaks, altered records, PrimerRegistro misuse, duplicate invoices,
cancellations of unknown invoices, timestamps going backwards, invalid NIF/dates/amounts/TipoFactura.
continues_from: last fingerprint of the previous batch, to audit a chain in pieces. Up to 20,000 records.
last_huella is what the next record must link to.
Inputs: records (required), continues_from. Returns: object
Check a Spanish NIF / NIE / CIF control character. Free.
Inputs: nif (required). Returns: object
Audit VERI*FACTU XML exported by an invoicing program (RegFactuSistemaFacturacion, a SOAP envelope, or any XML holding RegistroAlta / RegistroAnulacion elements, in document order).
Validates RegFactuSistemaFacturacion against the official AEAT schema (SuministroLR.xsd) when present, then
runs every chain and fingerprint check of validate_invoice_chain. XML that holds no records is not charged.
Inputs: content, content_base64, continues_from. Returns: object
Legal deadlines for VERI*FACTU and mandatory B2B e-invoicing in Spain, with sources and what is still pending publication. Free.
Inputs: no named parameters. Returns: object
Compute the VERI*FACTU fingerprint (huella, SHA-256) of one invoicing record.
record (AEAT field names; snake_case aliases accepted): alta: IDEmisorFactura, NumSerieFactura, FechaExpedicionFactura (DD-MM-AAAA), TipoFactura (F1, F2, F3, R1-R5), CuotaTotal, ImporteTotal (as written in the XML, decimal point), FechaHoraHusoGenRegistro (AAAA-MM-DDThh:mm:ss+hh:mm). anulación (TipoRegistro="anulacion"): IDEmisorFacturaAnulada, NumSerieFacturaAnulada, FechaExpedicionFacturaAnulada, FechaHoraHusoGenRegistro. previous_huella: fingerprint of the previous record of the chain; empty for the first record. Returns the fingerprint, the exact string hashed and any field problems (an error means the AEAT would reject the record).
Inputs: record (required), previous_huella. Returns: object
Recent tool additions, removals, and schema changes observed during successful MCP inspections.
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Scored across 11 tools
Each tool targets a distinct artifact and action: hash one record, audit a JSON chain, audit an XML export, generate vs. check a QR, build vs. validate Facturae, check a NIF. The cluster verifactu_hash / validate_invoice_chain / validate_verifactu_xml is related but differentiated by input (single record, JSON array, XML file), and the descriptions make the boundaries explicit. Only slight residual risk that an agent picks validate_invoice_chain when it actually has XML, or verifactu_hash when it wants the whole chain.
The dominant pattern is verb_noun (validate_invoice_chain, validate_verifactu_xml, validate_facturae, validate_nif, generate_verifactu_qr, build_facturae, check_qr_url). However verifactu_calendar and verifactu_hash are resource-first with no verb, and pricing / credits_balance are bare nouns, so conventions are mixed. Still readable overall, but not a predictable single scheme.
11 tools is well inside the comfortable range and every tool earns its place: four free utility/meta tools (calendar, pricing, balance, NIF) plus seven paid domain operations. No obvious redundancy or filler.
The surface covers the full compliance lifecycle for Spanish e-invoicing: NIF validation, record hashing, chain and XML auditing, QR generation and verification, and Facturae build/validate with XSD checks. Minor gaps: there is no tool to emit the full VERI*FACTU submission XML or sign documents, and QR checking has no counterpart image-decoding step, but these are reasonably out of scope and workable around.
Spanish Veri*factu invoicing: create invoices, expenses and VAT returns from your AI assistant.
Spanish e-invoicing with VeriFactu (AEAT): issue invoices, manage customers, validate NIFs.
Free no-auth tools for Spain: validate IBAN, EU VAT check (VIES), Modelo 303 sums, Veri*factu dates.
Invoicing your AI agent runs for you: invoices, quotes, expenses, VAT books. Veri*factu for Spain.
