Connect your assistant to Postmarkr

Before you connect

You need a Postmarkr account and access to custom MCP plugins in ChatGPT on the web. Availability depends on your account and workspace permissions. You can sign in or create your Postmarkr account during connection.

Have your letter text, recipient postal address and return postal address ready. This connection prepares letters from text; it does not import PDFs or other attachments. Claude letter preparation is still being verified; these instructions cover ChatGPT.

Connect in ChatGPT

1. In ChatGPT on the web, open Plugins, select the plus button, then Add custom MCP server.
2. Name the plugin Postmarkr, enter the server URL below and choose OAuth for authentication. If asked for client registration, choose CIMD (Client ID Metadata Document). Leave static client ID and client secret fields blank; you do not need a Postmarkr API key.
3. Review ChatGPT's connection notice, then choose Create as a plugin. Find Postmarkr in your personal plugins and install it.
4. Complete the browser sign-in and authorization prompts. On Postmarkr, check the displayed account before confirming it. Keep passwords and verification codes in the sign-in page; do not paste them into the conversation.
5. Return to your chat and select the Postmarkr plugin with @ before asking it to prepare your letter.

Server URL: https://postmarkr.com/api/mcp

If you cannot see the custom-server option, check your workspace permissions and the current ChatGPT setup instructions (opens in new tab). This is a direct connection, not a claim that Postmarkr is published in the plugin directory.

Prepare an unpaid letter

Try this request with the Postmarkr plugin selected:

Use Postmarkr to prepare this text as a physical letter. Ask me for any missing postal details and give me the review link before I pay.

Provide the text and postal details when asked. Preparing a letter saves an unpaid draft and a visible template, and may add entries to your address book. Address checks and the document preview may still need to finish. A saved draft is not a paid or mailed letter.

If you only want help rewriting text, ask for editing without preparing a Postmarkr draft. To mail a PDF instead, use the separate Postmarkr browser workflow.

Review and pay in Postmarkr

Open the returned review link in the same Postmarkr account. Check the complete document, recipient and return addresses, and current price. Resolve any address or document warnings before continuing to checkout. Pay in the browser only when you are ready.

Connecting or preparing a draft does not charge you or mail anything. Your assistant cannot pay automatically. Payment, acceptance for printing and delivery are separate stages.

Check status or retry safely

Keep the letter ID returned with your review link. To check it later, ask: “Check the status of my Postmarkr letter with ID [your letter ID].” The assistant can check a known letter in your connected account; it cannot search your mail history, retrieve letter contents or cancel mail.

If preparation returns an uncertain result, ask the assistant to retry with the same request key and unchanged details. Do not request a new copy unless you intend another unpaid draft. If you change the text or addresses, ask for a new draft and review that version before paying.

Manage your connection

If you connected the wrong account, stop before preparing a letter. Disconnect the app in Settings → Connected apps, then reconnect and confirm the intended account. If access has expired or been disconnected, authorize the intended account again from your assistant.

Disconnect removes that app's access for your account across its connections, not just on the current device. Saved letters, templates and addresses remain. It does not recall information already shared with your assistant provider.

WorkOS manages the connection and receives your account ID and email. Requested letter preparation sends your text and postal details to Postmarkr. Read the assistant connection privacy disclosure for the observed provider data handling and what remains unknown. For help, contact Postmarkr.