How to Connect Datev to Gemini — via MCP

Connect DATEV to Gemini

DATEV is the accounting software most German tax consultancies (Steuerberater) work in. With AnythingMCP, Gemini can read your DATEV Mandanten and their DATEV Unternehmen online (DUO) document settings through DATEV's official Online APIs, and you ask for them in plain language instead of clicking through DATEV.

The connector is read-only today: six tools for client master data and document metadata. It does not post bookings, read payroll or upload receipts (see the FAQ below).

What you can ask Gemini

• "List all Mandanten I have access to in DATEV." Uses datev_list_clients.
• "Show the master data for Müller GmbH: consultant number, client number, address." Uses datev_list_clients to find the Mandant, then datev_get_client.
• "Which of my Mandanten use DATEV Unternehmen online for documents?" Uses datev_documents_list_clients.
• "Which document types (Belegtypen) are set up for Müller GmbH?" Uses datev_list_document_types.
• "Which file types can Müller GmbH upload to DUO, and which DUO version are they on?" Uses datev_get_duo_version.
• "Compare my client list with the DUO list and tell me who has no DUO access yet." Uses datev_list_clients and datev_documents_list_clients.

What you need

• An app on the DATEV developer portal, created as a confidential client with the OpenID Connect Authorization Code Flow. Its redirect URI is https://cloud.anythingmcp.com/api/mcp-oauth/callback on AnythingMCP Cloud, or <your AnythingMCP URL>/api/mcp-oauth/callback if you self-host.
• Subscriptions to two API products for that app: accounting:clients 2.0 and accounting:documents 2.0.
• The app's client ID and client secret, which go into DATEV_CLIENT_ID and DATEV_CLIENT_SECRET. The portal shows the secret only once, so copy it in full.
• A DATEV-Konto user with SmartLogin or SmartCard/mIDentity. DATEV has no machine-to-machine access for these APIs: every call runs on behalf of a real DATEV user, and Gemini sees only the Mandanten that user may see.
• DATEV's production approval for live data. Every new DATEV app runs in the sandbox until DATEV approves it. Until then, use the DATEV Online APIs (Sandbox) connector, which is set up for DATEV's test data.

Step 1 — Create the DATEV app

Register at the DATEV developer portal, create the app as described above, subscribe it to accounting:clients 2.0 and accounting:documents 2.0, and note the client ID and secret.

Step 2 — Install the DATEV connector

On AnythingMCP Cloud, open Connectors, pick DATEV Online APIs (or the Sandbox variant) and paste the client ID and secret.

To self-host instead, start AnythingMCP with Docker and install the connector from the store at http://localhost:3000/connectors/store:

curl -fsSL https://raw.githubusercontent.com/HelpCode-ai/anythingmcp/main/docker-compose.quickstart.yml -o docker-compose.yml
printf 'JWT_SECRET=%s\nENCRYPTION_KEY=%s\n' "$(openssl rand -hex 32)" "$(openssl rand -hex 32)" > .env
docker compose up -d

Step 3 — Sign in with your DATEV-Konto

On the connector page, click Authorize with Provider and log in with your DATEV-Konto. AnythingMCP stores the refresh token encrypted and renews access tokens on its own. Confidential DATEV clients get rolling refresh tokens that last two years. Every call then carries the access token and the X-DATEV-Client-Id header that DATEV requires; you don't set either by hand.

Step 4 — Add it to Gemini

Your server URL: in AnythingMCP, open MCP Servers → the server this connector is on, and copy its URL (https://cloud.anythingmcp.com/mcp/…). Use it wherever this guide shows YOUR_SERVER_ID.

Gemini CLI reads MCP servers from ~/.gemini/settings.json (on Windows %USERPROFILE%\.gemini\settings.json). Add:

{
  "mcpServers": {
    "anythingmcp": {
      "httpUrl": "https://cloud.anythingmcp.com/mcp/YOUR_SERVER_ID",
      "headers": { "X-API-Key": "YOUR_MCP_API_KEY" }
    }
  }
}

1. Create an MCP API key in AnythingMCP under MCP Servers → your server → API keys, and paste it in place of YOUR_MCP_API_KEY.
2. Save the file and restart gemini.
3. Run /mcp inside Gemini CLI (or gemini mcp list in your shell) — anythingmcp should show as connected.
4. Start prompting — Gemini CLI can now call the DATEV tools.

Available tools

Every per-client tool takes the Mandant's UUID as clientId. Gemini gets it from datev_list_clients; it is not the same thing as your app's DATEV_CLIENT_ID.

Troubleshooting

• The DATEV login works, but the connection still fails. The token exchange after the login needs the exact client secret. DATEV expects it via HTTP Basic, which the connector does for you, so the usual cause is a secret that was copied incompletely or belongs to a different app. Create a new secret in the portal, paste it again and click Authorize with Provider once more.
• Calls are refused although you are signed in. Check in the portal that the app is subscribed to both accounting:clients 2.0 and accounting:documents 2.0. The document tools need the second one.
• The sandbox works, production does not. Your app has no production approval yet. Stay on the Sandbox connector until DATEV approves the app, then switch to DATEV Online APIs with the same credentials.
• A Mandant is missing. datev_list_clients returns only the Mandanten your DATEV user has rights for, and datev_documents_list_clients only those with active DUO access. Check the user's rights in DATEV rather than the connector.

FAQ

Can Gemini post bookings or upload receipts to DATEV? No. The connector reads client master data and document settings only. Uploading receipts to DUO needs binary file uploads that the connector engine does not handle yet, and bookings, payroll (Lohn) and DMS are separate DATEV API products that this connector does not cover.

Is it free? AnythingMCP is open source under AGPL-3.0, so self-hosting is free, including commercial use inside your own company. AnythingMCP Cloud comes with a 7-day free trial. Access to DATEV itself is governed by your DATEV contract and the developer portal's terms.

Is my data stored by AnythingMCP? Your DATEV client secret and refresh token are stored encrypted (AES-256-GCM) in your workspace and are never shown to Gemini. When Gemini uses a tool, AnythingMCP calls DATEV and passes the result to Gemini, and the call is recorded in your workspace's audit log. AnythingMCP Cloud is hosted in Frankfurt, Germany; if the data must stay on your own infrastructure, self-host AnythingMCP.

Where does Gemini CLI look for MCP servers? In ~/.gemini/settings.json for your user, or in .gemini/settings.json inside a project. gemini mcp list shows each server and whether it connects.

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