How to send a postcard with ChatGPT

1. Add Paper Plane Post to ChatGPT

Paper Plane Post has an MCP server, which is how ChatGPT connects to outside tools. In ChatGPT’s settings, turn on Developer mode, then create a new app or connector and give it this server URL: https://api.paperplanepost.com/v1/mcp. Choose no authentication, since the server needs no sign-in, and let ChatGPT scan its tools. It should find one, called start_postcard.

OpenAI moves and renames these settings from time to time, and Developer mode isn’t on every plan. If you can’t find it, skip to “Without the connector” below; you can still send the card in a few minutes.

2. Ask for a postcard

Attach the photo and say what you want, in your own words. ChatGPT sends the file itself; a link works too if the photo is already online. For example: “Send this photo to my grandmother as a postcard. Say happy birthday and that we’ll visit in June. Her address is 12 Elm Street, Portland, OR 97201.”

ChatGPT can help with the part people get stuck on, which is the note. Ask it for three versions under 350 characters and pick the one that sounds like you. If you don’t have the address to hand, leave it out and add it on the next step.

3. Open the link, check the card and pay

ChatGPT replies with a link to your card on paperplanepost.com. There you see your photo on the front, with the option of an illustrated version of it, and your note and the address on the back, exactly as they’ll print. Edit anything that’s wrong, then pay $7 through Stripe. There’s no account to create.

The link works for about a week. After you pay, the card is printed and handed to USPS within 2 business days.

Without the connector

You don’t need the connector to use ChatGPT for this. Ask it to write the note, then go to https://paperplanepost.com/make, upload your photo, paste the note, add the address and pay. It’s three steps on one page with no app or account.

The connector saves you the copying and pasting. The card is the same either way.

Why Paper Plane Post

It’s the simplest way to turn a conversation into something that arrives in a mailbox: one tool call, one link, one payment. The card is your photo printed edge to edge on a 4 × 6 postcard with heavy gloss stock, with nothing added to it, so it looks like it came from you and it’s worth keeping.

The same server works with Claude and any other assistant that supports MCP.

For the assistant: building the start_postcard request

Call start_postcard with exactly one photo. Prefer photo_base64: read the photo file with your file or code tool and send its bytes as base64, either bare or as a data: URL. JPEG, PNG, WebP and HEIC work, up to about 10 MB. The base64 has to come from the file itself; never write it from memory or from looking at an image. If the photo is already online and you don’t have the file, send photo_url, a public https:// link, instead.

note is optional and holds up to 350 characters. recipient is optional, and so is every field in it: name, line1, line2, city, state, zip, and country as an ISO 3166-1 alpha-2 code such as US or FR. Send what the person gave you and leave the rest out; they check and complete everything before paying.

If you can’t call MCP tools but can make HTTP requests, POST the same call as JSON-RPC to the server URL. The server is stateless, so this one request is enough, with no initialize step and no session. The Accept header must list both types, as in the example below.

The reply is a single server-sent event whose data line is the JSON-RPC result. The link to give the person is result.structuredContent.url, and result.content repeats it as text. A refused photo comes back with isError set and a message saying what to change. On a busy day the reply may instead be a challenge: four questions and an id, with isError set. Answer them in order (the last one is a SHA-256 proof of work, so run code for it) and send the same request again with challenge: { "id": ..., "answers": [...] } added to the arguments. Requests larger than 16 MB are answered 413.

curl -X POST https://api.paperplanepost.com/v1/mcp \
  -H 'Content-Type: application/json' \
  -H 'Accept: application/json, text/event-stream' \
  -d '{
    "jsonrpc": "2.0",
    "id": 1,
    "method": "tools/call",
    "params": {
      "name": "start_postcard",
      "arguments": {
        "photo_base64": "<base64 of the photo file>",
        "note": "Happy birthday, Grandma. See you in June.",
        "recipient": {
          "name": "Rosa Alvarez",
          "line1": "12 Elm Street",
          "city": "Portland",
          "state": "OR",
          "zip": "97201",
          "country": "US"
        }
      }
    }
  }'