PixelLetter MCP

Local MCP server (stdio) for thePixelLetterHTTPS interface. Hand it a PDF and a destination country and PixelLetter prints, folds, franks and posts the letter, optionally as registered mail. It also sends faxes, cancels orders, reads the account balance and drives the electronic invoice signature.

It pairs withpdf-letter-mcp: that server writes a DIN 5008 letter PDF, this one puts it in the post.send_lettertakes the absolute path thatcreate_letterreturns.

The implementation follows the published documentation: the HTTPS handbook, the e-mail handbook, the two signature handbooks, the reference PHP class (version 2.01) and the public error code list. Three values are not printed in those documents, colour printing, GoGreen postage and the NODUPLEX switch, and they are taken from thehudora/pyPostalclient that has been sending real orders with them. They are marked as such in the table below. Nothing else is invented.

claude mcp add pixelletter \ --env PIXELLETTER_EMAIL=you@example.com \ --env PIXELLETTER_PASSWORD=your-password \ -- node "/absolute/path/to/pixelletter-mcp/dist/src/index.js"

{ "mcpServers": { "pixelletter": { "command": "node", "args": ["/absolute/path/to/pixelletter-mcp/dist/src/index.js"], "env": { "PIXELLETTER_EMAIL": "you@example.com", "PIXELLETTER_PASSWORD": "your-password", "PIXELLETTER_DEFAULT_DESTINATION": "DE" } } } }

Credentials are only read from the environment, nothing is stored in the repository and nothing is written to disk.

{ "testMode": true, "files": ["/Users/you/Documents/Briefe/2026-07-24-widerspruch.pdf"], "destination": "DE", "transaction": "widerspruch-4711" }

Registered mail with return receipt, printed in colour on one side only:

{ "testMode": false, "files": ["/Users/you/Documents/Briefe/kuendigung.pdf"], "destination": "DE", "registered": true, "returnReceipt": true, "colorPrint": true, "duplex": false }

Plain text, typeset by PixelLetter, with the signature stored in the account:

{ "testMode": true, "address": ["Erika Mustermann", "Musterstr. 28", "81237 Musterstadt", "Deutschland"], "subject": "Ihre Anfrage vom 12.07.2026", "text": "Hallo Frau Mustermann,\n\nvielen Dank für Ihre Anfrage.\n\nMit freundlichen Grüßen\n\n%Unterschrift%\nMax Mustermann", "destination": "DE" }

Rules the tool enforces before anything is sent:

- One order carries either documents or text, not both. Several documents are converted and merged into one letter, in the order given.
- The destination country is mandatory for letters, a wrong code leads to wrong postage.
- The recipient address has to be visible in the address window area of the document, PixelLetter checks this before dispatch.
- Allowed upload types are.pdf,.doc,.xls,.ppt,.rtf,.wpd,.psd, 50 MB maximum. Error 053 shows that PixelLetter can restrict this to PDF, so PDF is the safe choice.
- Additional services, colour print and duplex are letter only, a pure fax order rejects them. Codes 28 (return receipt) and 29 (personal delivery) need 27 (registered), code 30 (drop-in registered) stands alone. Registered mail is a German product, other destinations run into error 026.

Full coverage of the fields the interface documents. "Applies to" says which dispatch type accepts the option, invalid combinations are rejected before the request goes out.

get_interface_referencereturns the same list at runtime, including the full error code table.

Named explicitly, because their absence is a property of the API and not an omission of this server:

- No job list.There is no documented call that lists or queries submitted orders.cancel_orderworks on an order id from the confirmation e-mail,get_account_inforeports the balance, everything else lives in the PixelLetter customer area.
- No envelope or paper format, no postage class, no delivery speed, no cover sheet, no reply envelope, no sender identification.These are no fields of the interface. Letters go into a DIN C6/5 window envelope and the postage follows weight and destination country.
- No address correction.Premiumadress shows up in error 088, but it has to be set up by PixelLetter support for the account and has no request field.
- Postcards, upload templates and bulk orders.The reference class and the error codes show they exist (font, template number, action 5), but no handbook documents their action values or their field layout. Sending a guessed action could produce a real, wrong dispatch, so they are left out.
- refin the auth block has no documented meaning and is always sent empty, exactly like the reference class does.

npm test # XML payloads, response parsing, option rules, configuration, HTTP layer with a mocked fetch

The tests never touch the live API. The HTTP layer is exercised through an injectedfetch, which checks the endpoint, thexmlfield, theuploadfileNparts, the test mode flag and the error code mapping.

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