MCP server · for AI agents

The way AI agents send physical mail.

Mailsnail lets Claude, Cursor, and any MCP client send real letters and certified mail. Add one server, sign in from your client, and your agent can put paper in a mailbox.

Get startedSee how it works
Claude Code
claude mcp add -t http mailsnail https://api.mailsnail.dev/mcp

Then run /mcp and sign in. In Cursor? Add it in one click. Claude, ChatGPT, VS Code, Codex and self-hosted setup →

From tool call to mailbox in four steps

No printers, no postage, no envelope-licking. No API keys to provision.

1

Add the server

One line in Claude Code or Codex, one click in Cursor or VS Code, or paste the URL into Claude or ChatGPT. Nothing to install.

2

Sign in from your client

Your client hits the server, gets pointed at our sign-in page, and registers itself. You approve it in the browser once.

3

Pay for the letter or fund a balance

If your balance can’t cover a send, you get two Stripe links: pay for just that letter by card, or add funds to a balance. Pay, then retry. Your card isn’t saved unless you opt in to auto-reload. Stripe handles the card — we never see the number.

4

It arrives in their mailbox

We render, print, fold, stamp, and hand to USPS. The recipient holds something physical — sent by software.

Get started

Tools your agent gets

Well-typed, and discoverable through llms.txt and /openapi.json.

preview_letter

Generate a proof PDF and the exact price WITHOUT charging or mailing. The recommended first step: preview, show the user, then send_letter with the returned draft_id.

send_letter

Mail a physical letter to any US address. Pass `body_text` (we render the PDF) or `file_url` (your own PDF). `extra_service: "certified"` for certified mail with tracking.

verify_address

USPS address validation. Free. Run this before sending so you stop paying for return-to-sender mail.

get_balance

Balance, saved card, and auto-reload settings. Free. Lets an agent check it can afford the job before it starts.

turn_off_auto_reload

Turns off automatic charges to your saved card and keeps the card on file. Free. Auto-reload is opt-in, and this is the off-switch.

get_letter

Look up status for any piece: queued, in_production, in_transit, delivered. Certified mail includes the USPS tracking number.

cancel_letter

Changed your mind? Cancel before printing starts, usually within about a day, and get the full price back on your balance.

Plus add_payment_method for funding your balance. Running it yourself against your own Click2Mail or Lob account adds list_letters — see self-hosted setup.

What agents actually mail

Customer thank-you notes

Your support agent autonomously drops a note in the mail after a positive interaction.

Legal notices & compliance mail

Preliminary notices, lien letters, and regulated correspondence that legally have to go on paper — with certified tracking and a signed return receipt when you need proof of delivery.

Personal post from your AI

Birthday cards, condolence letters, RSVP replies — the things humans should send but never get around to.

Cold outreach with proof

Targeted physical mail to the 50 people who actually matter, written and dispatched by an agent.

Step-by-step guides

What to write, how to prove it arrived, and what it costs.

Send a demand letterSend a debt validation letterStop debt collector contact with a cease letterSend a security deposit demand letterDispute a credit report errorSend certified mail with a return receiptSend a letter from ChatGPTSend a letter from Claude, Cursor, or CodexDispute a credit card billing errorRequest repairs from your landlordAppeal a health insurance denialSend a construction preliminary notice
All 16 guides

Pay per piece. No subscription.

Everything is priced at our cost. These prices are from a prepaid balance. Paying for a single letter by card costs a little more, because that one payment carries Stripe's whole processing fee.

from $1.21
First-class letter
$1.51 for one letter by card
from $8.61
Certified letter
$8.83 for one letter by card
from $11.64
Certified + electronic return receipt
$11.83 for one letter by card
from $14.27
Certified + green-card return receipt
$14.42 for one letter by card

One page, black and white; extra pages and color are priced at our cost. preview_letter quotes the exact price before anything is charged. Unspent balance is refundable — how billing works.

How these prices compare with fourteen other services

Built to be used by agents

If a model is reading this site cold, it can self-onboard in under a minute.

/llms.txt

Tight, machine-readable summary of what this server does and how to call it.

/llms-full.txt

Full docs in one file: tool schemas, examples, MCP config, and pricing.

/openapi.json

OpenAPI 3.1 spec for direct HTTP integration if MCP isn't available.

/setup

Copy-pasteable wiring for Claude Code, Claude Desktop, Cursor, Codex, and anything else that speaks MCP.

Give your agent a return address.

Add the server, sign in, and your agent can mail its first letter.

Get startedRead the full docs