Card Mailer

npx add-mcp 'https://cards.onmax.me/mcp/claude'

Card Mailer connector docs for Claude and ChatGPT

How to connect Card Mailer to Claude or ChatGPT, what each tool does, limits, privacy and troubleshooting.

Canonical: https://cards.onmax.me/docs/claude

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 required fields and US format, and returns a list id, whether USPS verification ran, 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.

Privacy

Addresses are used only to print and mail the cards and are deleted 30 days after the send date. See the privacy policy. Support: cards@onmax.me.