Einvoicing Core MCP Server

mcp-einvoicing-core

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Topics: mcp mcp-server e-invoicing electronic-invoicing python fastmcp peppol en16931 ubl fatturapa xp-z12-013 nfe xml base-library

Base package for electronic invoicing MCP servers.

Provides shared Pydantic models, EN 16931 invoice tree, UBL/CII wire format serializers, an OAuth2 HTTP client, Peppol SMP lookup, digital signature primitives, and a compliance audit framework so country-specific packages share a common foundation without duplicating code.

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What this package provides

Country packages

Installation

pip install mcp-einvoicing-core

For the compliance audit framework (used by country package CI):

pip install mcp-einvoicing-core[audit]

For XSLT 2.0/3.0 Schematron validation (SaxonSchematronValidator — needed for Schematron rule sets using XPath 2.0+ constructs, e.g. FNFE-MPE Factur-X 1.08 / ZUGFeRD):

pip install mcp-einvoicing-core[xslt2]

Configuration

Architecture

Country packages subclass the core abstractions and register their tools on a shared or standalone MCP server:

mcp-einvoicing-core
  ├── EN16931Invoice / InvoiceDocument  ← canonical invoice models
  ├── EN16931CreditNote                 ← credit note (type codes 381/383/384/385)
  ├── EN16931UBL/CII Serializer/Parser  ← wire format round-trip
  ├── convert_wire_format               ← CII ↔ UBL conversion
  ├── BaseDocumentGenerator/Validator/Parser/LifecycleManager
  ├── BaseEInvoicingClient              ← async HTTP (OAuth2/mTLS/bearer/API key/JWS)
  ├── PeppolSMPClient                   ← participant lookup via SMP/SML
  ├── PeppolTransmitter                 ← AS4 outbound transmission
  ├── BaseDocumentSigner                ← XAdES-EPES / XMLDSig
  ├── BaseEnvironmentEndpoints          ← sandbox/production URL routing
  ├── RoutingIdentifier                 ← country-specific routing ID validation
  ├── EInvoicingMCPServer               ← plugin registry wrapping FastMCP
  └── Audit framework                   ← per-package compliance checks

Plugin registration pattern

Country packages register their tools on a shared or standalone FastMCP instance:

# Standalone
from fastmcp import FastMCP
mcp = FastMCP(name="mcp-fattura-elettronica-it", instructions="...")
register_header_tools(mcp)
register_body_tools(mcp)
register_global_tools(mcp)

# Multi-country (optional EInvoicingMCPServer)
from mcp_einvoicing_core import EInvoicingMCPServer
server = EInvoicingMCPServer(name="mcp-einvoicing-eu", instructions="...")
server.register_plugin(register_header_tools, "it-header")
server.register_plugin(register_flow_tools, "fr-flow")
server.run()

Core also ships its own mountable Peppol tool plugin so country packages stop reimplementing SMP lookup and AS4 send. Supply a national identifier adapter (a small function that normalizes a bare national number, e.g. a VAT number, into a Peppol "<scheme>:<value>" participant ID):

from mcp_einvoicing_core.peppol.tools import register_peppol_tools

def be_id_adapter(identifier: str) -> str:
    if ":" in identifier:
        return identifier
    return f"0208:{normalize_vat_be(identifier)[2:]}"  # KBO/BCE scheme

server.register_plugin(
    lambda m: register_peppol_tools(m, id_adapter=be_id_adapter), "peppol"
)

This registers peppol_lookup_participant, peppol_get_service_endpoint, resolve_peppol_dns, peppol_send, peppol_directory_search, and 8 OpenPeppol eDEC code list tools (see Configuration above for EINVOICING_PEPPOL_CODELIST_DIR, required for the code list tools). Separate mountable plugins cover the EN 16931 semantic code lists (en16931_codelist_tools.register_en16931_codelist_tools), Peppol reporting (peppol.reporting_tools.register_peppol_reporting_tools), and MLS (peppol.mls_tools.register_peppol_mls_tools).

Claude Desktop / Cursor / Kiro compatibility

Existing configurations for country packages require no changes: tool names, signatures, environment variables, and entry points (server:main) are fully preserved.

License

Apache 2.0 -- see LICENSE.