mcp-einvoicing-be 🇧🇪

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Introduction

mcp-einvoicing-be is an MCP (Model Context Protocol) server that exposes tools for Belgian electronic invoicing. It covers the full Belgian e-invoicing ecosystem: Peppol BIS Billing 3.0, UBL 2.1, and the Mercurius network for public-sector invoicing. The server is part of the mcp-einvoicing-* family of country-specific servers, all built on top of mcp-einvoicing-core, which provides the shared validation engine, UBL abstractions, and Peppol network utilities.

Installation

Requirements

• Python ≥ 3.11
• mcp-einvoicing-core (installed automatically as a dependency)

Using uv (recommended)

uv add mcp-einvoicing-be

Using pip

pip install mcp-einvoicing-be

From source

git clone https://github.com/cmendezs/mcp-einvoicing-be.git
cd mcp-einvoicing-be
uv sync --all-extras

Configuration

Environment variables

The EUSR/TSR reporting and MLS tools additionally require the [xslt2] extra (pip install "mcp-einvoicing-be[xslt2]") for Schematron validation.

Claude Desktop integration

To use this server with Claude, add this configuration to your claude_desktop_config.json file:

{
  "mcpServers": {
    "einvoicing-be": {
      "command": "uvx",
      "args": ["mcp-einvoicing-be"],
      "env": {
        "BCE_API_KEY": "your-bce-api-key",
        "PEPPOL_ENV": "production"
      }
    }
  }
}

For a local development install:

{
  "mcpServers": {
    "einvoicing-be": {
      "command": "uv",
      "args": ["run", "mcp-einvoicing-be"],
      "cwd": "/path/to/mcp-einvoicing-be"
    }
  }
}

Cursor integration

Cursor supports MCP servers via stdio. Add the configuration in:

• Global (all projects): ~/.cursor/mcp.json
• Project (this repository only): .cursor/mcp.json

{
  "mcpServers": {
    "einvoicing-be": {
      "command": "uvx",
      "args": ["mcp-einvoicing-be"],
      "env": {
        "BCE_API_KEY": "your-bce-api-key",
        "PEPPOL_ENV": "production"
      }
    }
  }
}

Reload the Cursor window (Ctrl+Shift+P then Reload Window) to apply the changes.

Kiro integration

Kiro supports MCP servers via its dedicated configuration file. Two levels are available:

• Global (all projects): ~/.kiro/settings/mcp.json
• Workspace (this repository only): .kiro/settings/mcp.json

{
  "mcpServers": {
    "einvoicing-be": {
      "command": "uvx",
      "args": ["mcp-einvoicing-be"],
      "env": {
        "BCE_API_KEY": "your-bce-api-key",
        "PEPPOL_ENV": "production"
      },
      "disabled": false,
      "autoApprove": []
    }
  }
}

The file is automatically reloaded on save. You can also open the config via the command palette (Cmd+Shift+P / Ctrl+Shift+P) then MCP.

Kiro security tip: rather than writing secrets in plain text, use the syntax "BCE_API_KEY": "${BCE_API_KEY}", Kiro resolves shell environment variables at startup.

Available tools

validate_invoice_be

Validates a UBL 2.1 XML invoice. The peppol-bis-3/pint-eu profiles run real Schematron validation against the CEN EN 16931 base rules (~50 BR-* structural/arithmetic rules, via mcp-einvoicing-core's bundled base Schematron — see CHANGELOG.md v0.8.0). This does not check the Peppol-specific overlay rules (no confirmed OpenPeppol redistribution rights); results carry an explicit en16931-base-only scope warning and should not be read as full Peppol BIS3 conformance. The mercurius profile runs the Mercurius-specific overlay (endpoint scheme, PO reference) but does not check base EN 16931/Peppol BIS 3.0 compliance.

Returns a ValidationResult with valid, errors, and warnings (each carrying the failed rule ID and a human-readable message).

generate_invoice_be

Generates a valid UBL 2.1 Belgian e-invoice XML document from structured data.

The InvoiceInput object supports:

{
  "invoice_number": "INV-2024-001",
  "issue_date": "2024-01-15",
  "due_date": "2024-02-14",
  "currency_code": "EUR",
  "supplier": { "name": "...", "vat_number": "BE0428759497", "address": {...} },
  "customer": { "name": "...", "vat_number": "BE0403170701", "address": {...} },
  "lines": [{ "description": "...", "quantity": 1, "unit_price": 100.00, "vat_rate": 21.0 }]
}

Returns a UBL 2.1 XML string.

transform_to_ubl

Converts a structured JSON invoice payload to UBL 2.1 XML without full validation. Useful as a first step before validation.

lookup_vat_be

Looks up a Belgian enterprise number (VAT number) against the BCE/KBO public database.

Returns enterprise name, registered address, legal status, and NACE activity codes.

Peppol network tools

Peppol participant lookup, service-endpoint lookup, a DNS-only diagnostic, AS4 send, Peppol Directory search, and the OpenPeppol eDEC codelist tools are provided by the shared core Peppol tool plugin (mcp_einvoicing_core.peppol.tools.register_peppol_tools), mounted in server.py with a BE-specific identifier adapter: a bare Belgian VAT number (e.g. 0428759497 or BE0428759497) is normalized to the 0208:<digits> Peppol scheme (KBO/BCE enterprise number); an already scheme-qualified identifier (e.g. 0208:0428759497) passes through unchanged.

peppol_send signs outbound messages with a real wsse:Security signature as of mcp-einvoicing-core v1.20.0 (previously computed and discarded — see CHANGELOG.md v0.10.0).

See the mcp-einvoicing-core README for full parameter documentation on these tools.

Peppol reporting and status tools

Added in v0.10.0 via three opt-in core plugins, mounted unconditionally in server.py. Each raises a clear error at call time (not at registration) if its extra or data directory is missing.

See the mcp-einvoicing-core README for full parameter documentation on these tools.

parse_ubl_invoice_be

Parses a UBL 2.1 XML invoice (Peppol BIS 3.0) into a structured dict. Satisfies the mandatory reception capability required by Art. 13quater of Royal Decree no. 1.

Returns {"success": true, "invoice": {...}, "warnings": []} on success, or {"success": false, "error": "..."} on parse failure.

get_invoice_types_be

Returns the list of supported Belgian e-invoice document types (invoice, credit note, debit note) with their UBL customizationID and profileID values for each profile.

No input parameters required.

B2G via Mercurius

Mercurius is the Belgian federal public-sector e-invoicing platform. It operates as a Peppol network receiver, not a separate API. B2G invoices are submitted through the standard Peppol network using the authority's participant ID in the 0208 scheme (KBO/BCE 10-digit enterprise number). The Access Point routes the invoice to Mercurius automatically. No Mercurius-specific submission endpoint or API key is required.

Architecture

mcp-einvoicing-be/
├── src/
│   └── mcp_einvoicing_be/
│       ├── __init__.py
│       ├── server.py              # MCP server entry point & tool registration
│       ├── tools/
│       │   ├── __init__.py
│       │   ├── validation.py      # validate_invoice_be
│       │   ├── generation.py      # generate_invoice_be
│       │   ├── transformation.py  # transform_to_ubl
│       │   ├── parsing.py         # parse_ubl_invoice_be
│       │   └── lookup.py          # lookup_vat_be, get_invoice_types_be
│       ├── models/
│       │   ├── __init__.py
│       │   ├── invoice.py         # InvoiceInput, InvoiceLine, ValidationResult
│       │   └── party.py           # Supplier, Customer, Address
│       ├── standards/
│       │   ├── __init__.py
│       │   ├── peppol_bis_3.py    # Peppol BIS Billing 3.0 rules & customization IDs
│       │   ├── ubl.py             # UBL 2.1 namespace constants & XML helpers
│       │   ├── pint_be.py         # PINT-BE placeholder (removed in v0.4.0)
│       │   └── mercurius.py       # Mercurius network config & overlay rules
│       └── utils/
│           ├── __init__.py
│           └── helpers.py         # VAT number normalization, date formatting, etc.
├── tests/
│   ├── __init__.py
│   ├── conftest.py
│   ├── test_tools/
│   │   ├── __init__.py
│   │   ├── test_validation.py
│   │   ├── test_generation.py
│   │   └── test_transformation.py
│   └── fixtures/
│       ├── invoice_valid_peppol.xml
│       ├── invoice_valid_pint_be.xml
│       └── invoice_invalid.xml
├── .github/
│   └── workflows/
│       ├── ci.yml
│       └── publish.yml
├── pyproject.toml
├── CHANGELOG.md
├── CONTRIBUTING.md
└── LICENSE

Relationship to mcp-einvoicing-core

mcp-einvoicing-core provides:

• Shared UBL 2.1/2.3 XML parsing and serialization utilities
• EN 16931 base validation rules (syntax + semantic)
• Peppol network client (SMP lookup, SML resolution)
• Common Pydantic base models (BaseInvoice, BaseParty, BaseValidationResult)

mcp-einvoicing-be adds Belgium-specific logic on top:

• Mercurius network overlay rule validation (XPath-based) for B2G invoicing
• BCE/KBO enterprise database integration
• Belgian VAT number normalization (BTW/TVA format) and OGM/VCS check-digit validation
• UBL 2.1 invoice parsing for mandatory reception (Art. 13quater)
• customizationID and profileID values specific to the Belgian Peppol corner

Vendor neutrality

This server implements the standard itself: it builds, validates, and signs the document locally. It is not a client for a commercial invoicing platform, and your signing keys and credentials never leave your own infrastructure.

A Peppol access point is required, but any accredited access point speaks the same AS4 profile, so switching providers is a configuration change, not a code change.

Contributing

Contributions are welcome. Please open an issue to discuss significant changes before submitting a pull request.

git clone https://github.com/cmendezs/mcp-einvoicing-be.git
cd mcp-einvoicing-be
uv sync --all-extras
uv run pytest
uv run ruff check src tests
uv run mypy src

All pull requests must:

• Pass the full test suite (pytest)
• Pass linting (ruff check)
• Pass type checking (mypy)
• Include or update tests for any changed behaviour
• Reference the relevant rule ID(s) when fixing a validation issue

See CONTRIBUTING.md for full guidelines.

Other e-invoicing MCP servers

License

This project is licensed under the Apache 2.0 — see LICENSE for details. For the full version history, see CHANGELOG.md.