verifactu-mcp
Server Configuration
Describes the environment variables required to run the server.
| Name | Required | Description | Default |
|---|---|---|---|
| KEYFLINT_URL | No | URL of the Keyflint license server, e.g. https://licenses.keyflint.dev. | |
| KEYFLINT_LICENSE | Yes | Your Keyflint license key, e.g. "LIC-...". Used for authentication and credits. | |
| VERIFACTU_PRICES | No | Tool credit price overrides, e.g. validate_invoice_chain=5,build_facturae=4. | |
| VERIFACTU_MAX_BYTES | No | Maximum input size in bytes. Defaults to 10 MB. | 10 MB |
| KEYFLINT_PUBLIC_KEYS | No | Public keys used to verify licenses. | |
| KEYFLINT_CHECKOUT_URL | No | Checkout URL used to purchase licenses or credits. |
Instructions
Guidance the server publishes about itself, which clients place ahead of the tool catalog so the model reads it before choosing anything.
Spanish invoicing compliance checks, offline and stateless. validate_invoice_chain and validate_verifactu_xml recompute the SHA-256 fingerprint (huella) of every VERI*FACTU record (alta and anulación) exactly as the AEAT specifies, check that each record links to the previous one, and report breaks, altered records, bad NIFs, dates and amounts: use them to audit what any invoicing program exported. verifactu_hash computes one fingerprint. generate_verifactu_qr returns the AEAT tax QR URL and image (level M) with the printing rules. build_facturae turns plain invoice data into a Facturae 3.2.2 XML validated against the official XSD (unsigned: sign it with the issuer's certificate before sending to FACe). validate_facturae checks a Facturae file: XSD, arithmetic, NIFs, DIR3 codes, signature presence. Free: verifactu_calendar (legal deadlines in force), check_qr_url, validate_nif, pricing, credits_balance. Amounts use a decimal point. This server is not an invoicing system and sends nothing to the AEAT. Unreadable input is never charged; failures are refunded.
Capabilities
Features and capabilities supported by this server
Protocol revision2025-11-25
| Capability | Details |
|---|---|
| tools | {
"listChanged": false
} |
| prompts | {
"listChanged": false
} |
| resources | {
"subscribe": false,
"listChanged": false
} |
Tools
Functions exposed to the LLM to take actions
| Name | Description |
|---|---|
| verifactu_hashA | 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). |
| validate_invoice_chainA | Audit a VERI*FACTU chain of records (in generation order) given as JSON objects. Each record has the fields of |
| validate_verifactu_xmlB | 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 |
| generate_verifactu_qrA | 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. |
| build_facturaeA | 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 |
| validate_facturaeA | 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. |
| check_qr_urlB | Check a tax QR URL read from an invoice: official AEAT host, path, parameters and formats. Free. |
| validate_nifA | Check a Spanish NIF / NIE / CIF control character. Free. |
| verifactu_calendarA | Legal deadlines for VERI*FACTU and mandatory B2B e-invoicing in Spain, with sources and what is still pending publication. Free. |
| pricingA | Credit price of each tool and where to buy credits. Free. |
| credits_balanceA | Remaining credits on your KeyFlint license. Free. |
Prompts
Interactive templates invoked by user choice
| Name | Description |
|---|---|
No prompts | |
Resources
Contextual data attached and managed by the client
| Name | Description |
|---|---|
No resources | |
TDQS
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.