Gofact MCP server

gofact

🇫🇷 Version française

Small Go binary that turns a print-ready HTML invoice into Factur-X: a compliant PDF/A-3 with the CII EN 16931 XML embedded, and optionally submits it to a French e-invoicing platform (PDP — plateforme de dématérialisation partenaire).

Built for the invoicing of a French freelancer or small business (the French e-invoicing reform), and also shipped as a Claude Code plugin with the creer-facture skill.

Pipeline

JSON  ──EN 16931 rules──▶  rejected if non-compliant (before producing anything)
      ──gofact──────────▶  factur-x.xml (CII EN 16931)
HTML  ──headless Chrome─▶  PDF          (identical to Ctrl+P output, backgrounds included)
PDF + XML ──pure Go─────▶  Factur-X     (PDF/A-3 + VERBATIM embedding of the XML)
Factur-X  ──self-check──▶  re-read      (structure + integrity of the embedded XML)

Verbatim embedding — important. The XML is embedded byte for byte.

An assembler that re-serializes it through its own model **loses extended

fields**, in particular the PDP electronic routing addresses (BT-34/BT-49).

gofact never touches the XML it has produced.

System dependencies

A browser, and that's it.

• Chrome, Edge, Brave or Chromium — HTML → PDF rendering

Auto-detected on Linux, macOS and Windows (where Edge is preinstalled, so nothing to do). Sandboxed packages — snap, flatpak — are skipped: they cannot read the temporary files gofact hands them. To point at a specific executable: GOFACT_CHROME or -chrome.

The PDF/A-3 assembly is done in Go (pdfcpu): no Ghostscript, no Java, no first-run download. The sRGB ICC profile is embedded in the binary.

Compliance

Two checks, at two different moments:

anything. gofact refuses to issue an invoice it knows to be non-compliant, reporting the rule identifier (BR-50, BR-CO-15…) and the field to fix.

• EN 16931 business rules, applied on the model before producing

structures are verified (/AF, /OutputIntents, XMP, /EmbeddedFiles) and the embedded XML is compared byte for byte with the one that was generated.

• PDF self-check, after writing: the file is re-read, the Factur-X

Deep PDF/A-3b compliance is verified by veraPDF, via Mustang, in continuous integration — never on the user's machine:

GOFACT_ORACLE_HTML=facture.html go test -tags=ci ./internal/facturx

Build

go build -o gofact .
go test ./...

Configuration

No identity and no secret is hard-coded. The invoice issuer, the payment IBAN and the PDP credentials come from the environment.

cp .env.example .env    # then fill in your own values

gofact loads, in order and without ever overwriting an already-defined variable: the file passed to -env, otherwise ./.env, then $XDGCONFIGHOME/gofact/.env (~/.config/gofact/.env by default). The .env is git-ignored — never commit it.

Shortened. The full README is on GitHub.