Your agent writes the letter. We post it.

No. Zetteldesk works with a prepaid balance: you top up from €10 by card, SEPA direct debit or PayPal through Stripe, and each letter is deducted when it is sent. No base fee, no minimum volume.

Any AI assistant or application that supports remote MCP servers with OAuth sign-in, for example Claude, Claude Code, ChatGPT, the Gemini CLI and Codex, as well as automation platforms such as Soforce. The steps for each client are in the “Connect” section.

Yes. An automation, for example in Soforce, generates the invoice PDF, checks it with validate_letter and sends it with send_letter. A fixed idempotency_key per invoice ensures that a repeated call does not send the letter twice. The automation queries the status with get_letter or list_letters. Payment comes from your balance, which you can have topped up automatically if you wish. Note: for invoices between businesses in Germany, the e-invoicing rules apply. Check whether a paper invoice is still permitted in your case; this is not legal advice.

You set this up once and it then runs on its own. In an automation platform such as Soforce you create a workflow that regularly looks at your list of open items, for example from your accounting or a spreadsheet. For each overdue invoice it creates a letter from your template and has it sent as a letter through Zetteldesk. It then writes the dispatch date back into your list.

You decide yourself after how many days of delay which stage goes out, from the friendly reminder to the formal dunning letter. The same reminder is never sent twice.

How to connect Zetteldesk to the platform is explained here.

Anything that regularly goes out as a letter can be set up as a workflow, for example in an automation platform such as Soforce. Typical examples:

• Invoices and credit notes to customers who do not receive e-invoices: the invoice from your accounting software goes out by post automatically.
• Payment reminders and dunning letters: as soon as an invoice is overdue, the matching letter is created from your template.
• Cancellation and contract letters: the letter is created from the contract data and sent.
• Confirmations and notices: a new order or a new registration triggers the letter automatically.
• Invitations and mandatory notices, for example for meetings: each recipient gets their own letter.
• Mail to authorities: applications and notifications that must be received in writing are created and sent.

You set up the workflow once in Soforce and connect it to Zetteldesk (instructions). Every letter is checked before it is sent, and your balance is only charged when it is sent.

Zetteldesk works with automation platforms such as Soforce that support remote MCP servers with OAuth sign-in. In Soforce:

• Open app.soforce.ai/apps and click "Add connection" under "MCP connections".
• Enter Zetteldesk as the name and the server URL from the Connect section as the "Server address".
• Choose "Sign in with Zetteldesk", sign in and confirm with Allow.

After that, your automations can call all Zetteldesk tools.

The sending tools are marked as destructive. Claude and ChatGPT therefore ask for your confirmation before every call. In addition, your agent can never spend more than your balance: the balance is a hard upper limit.

Every PDF is checked before we charge anything. If the print service provider later cannot read the address after all or reports a problem, the letter is marked as rejected and the full amount is automatically credited back to your balance.

Yes, as long as it has not gone to print yet: cancel it in the dashboard or have your agent call cancel_letter, and you get the full amount back. Once the letter has been handed over to printing and dispatch, it cannot be retrieved, just like a letter you have already dropped in the mailbox.

Zetteldesk is hosted in Germany. Uploaded PDFs are stored encrypted and deleted automatically after 90 days. The letters are printed and sent by our print and dispatch partner in Germany. We comply with the GDPR and, on request, conclude a data processing agreement (DPA) with you.

A4 portrait, with the recipient in the address field according to DIN 5008 on the first page, exactly as every German letter template provides anyway. If something does not fit, validate_letter tells your agent exactly what to correct.

The letters are printed and posted in Germany. Letters abroad are possible at the respective international postage rate. You will see the exact price before sending.

All prices include 19% VAT. For every top-up you receive a receipt from Stripe, and on the billing page every letter is listed with its price.