HOLCO FEC Controls

Deterministic, explainable controls for synthetic French accounting export (FEC-like) data, exposed as a local MCP server for Claude and other compatible clients.

Deterministic when possible. AI when necessary. Human when accountable.

This repository is a clean-room public example. It contains no production code, customer data, credentials or internal HOLCO endpoints. It is not tax advice and does not certify legal or fiscal compliance.

Controls

• required column presence;

• parseable YYYYMMDD dates;

• decimal debit and credit amounts;

• debit/credit balance for every journal entry;

• duplicate-line detection.

Every finding contains a stable code, severity, line or entry reference and a human-readable explanation. The AI client presents the result; it does not silently change the deterministic verdict.

Related MCP server: polyaccounts-demo

Control contract

The server separates planning from execution:

1. plan_fec_control declares controls, assumptions and decisions that require human input;

2. analyze_fec_text runs every applicable deterministic control;

3. the result binds evidence to the source with SHA-256 hashes and locators, without echoing accounting rows;

4. every planned control is reported as PASS, REVIEW, FAIL or NOT_RUN.

Business plausibility is deliberately NOT_RUN until an entity-approved policy or benchmark is provided. A generic model opinion cannot turn a failed accounting invariant into a pass. Consequently, a technically clean file has a deterministic_outcome of PASS but remains globally REVIEW while the declared business check is not run.

Run the tests

python -m pip install -e '.[mcp]'
python -m unittest discover -s tests -v

Connect to Claude Desktop

After installation, add this local server to your Claude Desktop MCP configuration:

{
  "mcpServers": {
    "holco-fec-controls": {
      "command": "holco-fec-mcp"
    }
  }
}

Restart Claude Desktop, then ask it to call analyze_fec_text with FEC content. The tool accepts text rather than a filesystem path, preventing unrestricted file reads by the server. Keep real accounting exports within an environment whose confidentiality rules you control.

MCP tools

• list_fec_controls: returns the public control catalogue.

• plan_fec_control: previews scope, assumptions and human decisions.

• analyze_fec_text: analyses tab-separated content and returns structured results, evidence hashes, completeness and the stop reason.

See examples/synthetic_fec.txt for a fictitious balanced entry.

Normative anchoring

The FEC (fichier des écritures comptables) is defined by article A.47 A-1 of the French Livre des procédures fiscales and the arrêté of 29 July 2013: 18 normative fields in a fixed order, YYYYMMDD dates, and a normalised file naming scheme. The DGFiP publishes an open-source structural checker, "Test Compta Demat" (CeCILL licence, official DGFiP GitHub repository); article 1729 D of the CGI defines the sanction for a non-compliant file.

The controls in this repository target a subset of that referential on synthetic data. Like the DGFiP checker itself, a green result is not an attestation of conformity and does not bind anyone: it is a reproducible technical statement about the supplied bytes. The full doctrine mapping of the HOLCO control framework is maintained in the companion repository holco-finance-controls (DOCTRINE.md).

Licence

MIT. Copyright © 2026 HOLCO INVEST.