Card Mailer
Prints 5x7 photo postcards with your message and mails them by USPS First-Class to a list of US addresses.
Hosted MCP Server
npx add-mcp 'https://cards.onmax.me/mcp/claude'Installs into Claude Code, Codex, Cursor and more
Documentation
Card Mailer connector documentation
Card Mailer prints 5×7 photo postcards and mails them USPS First-Class to a list of US addresses. These are the details for using it from Claude or ChatGPT.
Connect
- Claude: Settings → Connectors → Add custom connector. Name: Card Mailer. URL:
https://cards.onmax.me/mcp/claude. No sign-in. - ChatGPT: in developer mode with
https://cards.onmax.me/mcp, and from the ChatGPT directory once it is listed.
Tools
| Tool | What it does | Changes data |
|---|---|---|
import_address_list | Reads pasted text, CSV or XLSX addresses (up to 300), checks each against USPS data, and returns a list id and the rows to fix. | Creates a draft list |
fix_address | Corrects or removes one recipient by row number and checks it again. | Edits the draft list |
design_card | Builds the card: greeting and photo on the front, message and sign-off on the back. Takes an attached photo (ChatGPT) or a public image URL. Does not generate images. | Creates or edits a draft design |
quote_mailing | Price, send date and arrival window. Given an arrive-by date, it returns the latest safe send date. | No |
create_mailing | Creates an unpaid order and returns a link to https://cards.onmax.me/m/…, where the user reviews it and pays with Stripe in the browser. | Creates an unpaid order |
get_mailing_status | Paid, printing, mailed or delivered, with per-recipient counts. | No |
Nothing is printed, mailed or charged inside Claude or ChatGPT. Payment happens only on the order page.
Limits
- US addresses only, including APO/FPO and Puerto Rico.
- Up to 300 recipients per order.
- 5×7 postcards without envelopes, one design per order.
- Greeting up to 40 characters, message up to 500, sign-off up to 80.
- In Claude, attached images aren't passed to connectors: add the photo with the Upload a photo button in the card preview, or share a public link.
Example prompts
Make a holiday card from this photo (link) with "Wishing you a joyful season" and mail it to the addresses in this spreadsheet so they arrive before December 20.
Send a thank-you card to each client in this CSV, signed "The team at Oak & Pine Studio".
What would 25 cards cost to arrive by December 20?
Troubleshooting
- "list_id not found": lists are deleted 14 days after creation if no order is paid. Import the list again.
- A row says it could not be read: send name, street, city, state and ZIP for that row with
fix_address. - "Card Mailer mails only to US addresses": remove that row. International mail isn't offered.
- The photo is blurry: use a photo at least 2000 pixels wide.