DATEV EXTF

engineering.seamlessPublished by seamless.engineeringv0.1.0Updated Oct 24, 2026

Validate and write DATEV-Format (EXTF) files locally, with findings in German and English.

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Server details

Identifier: engineering.seamless/datev-extf
Transport: STDIO
Runtime: Desktop only
Trust: Verified
Published: Sep 26, 2026

Security note

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Overview

AI-generated overview

Local MCP server that validates and writes DATEV-Format (EXTF) booking and master-data files, explaining findings in German or English.

What you can do: Validate an EXTF file or pasted text, returning header data, error and warning counts, and each finding with line, field, value and explanation in German or English (encoding is only checked for files). Explain a finding code such as amount-dot or bu-automatic. Build a Buchungsstapel (format version 13) from a header and booking rows in cents, validate it, and write it as Windows-1252 to a path or return the CSV text. List the 125 Buchungsstapel or 254 Debitoren/Kreditoren columns by position. Resources expose column lists and finding texts; a prompt validates a file and proposes fixes for the export that produced it.
When to use it: Useful when a DATEV import is rejected and you want the reason per line and field, or when you want an assistant to turn a list of bookings into a file DATEV accepts. It checks format only, not bookkeeping correctness.
Requirements: Runs locally over stdio via the npm package, started with npx. Needs Node.js 20 or later. No account, API key or environment variable is required. Absolute file paths are safer because relative paths resolve against the server's working directory.

Before you install

The writer creates or overwrites the file at the given output path, so check that path before running it. It validates format only and cannot judge whether accounts or tax keys are correct, and it does not choose them; confirm those with a tax advisor. Not affiliated with DATEV.

Installation

In SourceWeft

Open DATEV EXTF in the dashboard and add it to a workspace.
Enable the server for the chats that should use its tools.

Desktop only via STDIO. STDIO servers start a local process, so they need the SourceWeft desktop host.

Other MCP clients

Follow the launch instructions in the repository.

README

datev-extf-mcp

[npm] [CI] [License: MIT]

MCP server that validates and writes DATEV-Format (EXTF) files: Buchungsstapel (booking batches) and Debitoren/Kreditoren (customer and supplier master data). Ask your AI assistant why DATEV rejected an import, or have it turn a list of bookings into a file DATEV accepts.

Deutsch: MCP-Server, der Dateien im DATEV-Format (EXTF) prüft und schreibt. Fragen Sie Ihren KI-Assistenten, warum DATEV einen Import ablehnt: Er bekommt jeden Fehler mit Zeile, Feld und einer verständlichen Erklärung, etwa Punkt statt Komma im Umsatz, fehlende führende Null im Belegdatum oder BU-Schlüssel auf Automatikkonten.

Local only. The server runs on your machine and reads files from disk. Nothing is uploaded, and there's no account or API key.
Built on @seamless-engineering/datev-extf. Its rules come from DATEV's own material: the Formatbeschreibung on developer.datev.de, the DATEV-Format Prüfprogramm and the #REW import messages.
Every file the writer produces passes the validator.

Prefer a browser? The same checks run in the DATEV EXTF validator (English), also without upload.

Install

Needs Node.js 20 or later.

Claude Code

Claude Desktop (claude_desktop_config.json), Cursor (.cursor/mcp.json) and most other clients:

json

{  "mcpServers": {    "datev-extf": {      "command": "npx",      "args": ["-y", "@seamless-engineering/datev-extf-mcp"]    }  }}

{  "mcpServers": {    "datev-extf": {      "command": "npx",      "args": ["-y", "@seamless-engineering/datev-extf-mcp"]    }  }}

Claude Desktop, one click: download datev-extf-mcp.mcpb from the latest release and open it. Build it yourself with ./scripts/bundle.sh.

Relative file paths resolve against the server's working directory, so absolute paths are the safer choice.

Tools

Tool	What it does
`validate_datev_extf`	Checks a file (`path`) or pasted text (`content`). Returns header data, error and warning counts, and each finding with line, field, value and an explanation in German (`lang: "de"`, default) or English (`"en"`). The encoding is only checked for files.
`explain_datev_finding`	Explains a finding code such as `amount-dot` or `bu-automatic`.
`write_buchungsstapel`	Builds a Buchungsstapel (Formatversion 13) from a header and booking rows (amounts in cents), validates it, and writes it as Windows-1252 to `outputPath` or returns the CSV text.
`list_datev_columns`	Lists the 125 Buchungsstapel or 254 Debitoren/Kreditoren columns by position.

Resources: datev-extf://columns/buchungsstapel, datev-extf://columns/debkred, datev-extf://findings/de and datev-extf://findings/en.

Prompt: fix_datev_import validates a file and proposes fixes for the export that produced it.

Example

Why does DATEV reject ~/Downloads/EXTF_Buchungsstapel.csv?

2 errors, 1 warning in 214 data rows (category buchungsstapel, encoding utf-8).- warning [utf8-without-bom]: The file is UTF-8 without a byte order mark. DATEV then reads it as Windows-1252 and umlauts turn into garbage …- error line 4 [amount-dot]: Amount “49.90” uses a dot as the decimal separator. DATEV expects a comma: 12.50 becomes 12,50.- error line 9 [date-leading-zero]: Document date “506” has only three digits: the leading zero is gone. …

2 errors, 1 warning in 214 data rows (category buchungsstapel, encoding utf-8).- warning [utf8-without-bom]: The file is UTF-8 without a byte order mark. DATEV then reads it as Windows-1252 and umlauts turn into garbage …- error line 4 [amount-dot]: Amount “49.90” uses a dot as the decimal separator. DATEV expects a comma: 12.50 becomes 12,50.- error line 9 [date-leading-zero]: Document date “506” has only three digits: the leading zero is gone. …

Not tax advice

The server checks format, not bookkeeping. It can't tell whether an account or tax key is right for a transaction, and it doesn't pick them when writing. Agree that with your tax advisor.

DATEV and DATEV-Format are trademarks of DATEV eG. This project is not affiliated with or endorsed by DATEV.

Maintenance

Maintained by seamless.engineering for our own production use: we run managed DATEV integrations for shops, payment providers and ERPs, fully EU-hosted. Issues and PRs welcome, no SLA.

Releasing

Bump version in package.json, both versions in server.json and the one in manifest.json, commit, then tag and push: git tag v0.1.1 && git push origin v0.1.1. The release workflow publishes to npm with provenance via trusted publishing, then to the MCP Registry as engineering.seamless/datev-extf.

MIT licence.

Source: README.md at commit 3bd7608

Tools

SourceWeft has not started this package in its sandbox yet, so its tools are not known.

Version history

v0.1.0LatestSep 26, 2026

Score

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