No account. No API key. Pay per call.

{
  "data": {
    "inbox_id": "6f1c2d3e-8a4b-4c5d-9e6f-0a1b2c3d4e5f",
    "email": "paid-bot_3e7a9c1d@box1.deadsimple.email",
    "display_name": "Paid Bot",
    "credentials": {
      "api_key": "dse_...",
      "key_id": "key_...",
      "account_id": "0b7d4a6e-2c19-4f8e-b3a1-5d6e7f8a9b0c",
      "note": "Use this key (Authorization: Bearer ...) for free reads and sends within the plan; or keep paying per request from the same wallet. Claim the account with a verified email via POST /v1/auth/claim to lift limits and add custom domains.",
      "warning": "Store this key now. It is shown once and cannot be retrieved again."
    },
    "payment": {
      "transaction": "0x9f3c...",
      "network": "eip155:8453",
      "payer": "0xAbCd...0001"
    }
  }
}

# Second paid inbox from the same wallet: same account, inbox_limit +1,
# no "credentials" block. With Stripe MPP, "payment" is {"reference": "pi_...", "method": "stripe"}.

# headers
PAYMENT-REQUIRED: <base64 of the JSON below, minus our error object>
WWW-Authenticate: Payment id="...", realm="api.deadsimple.email", method="stripe", intent="charge", expires="...", request="..."
Cache-Control: no-store
Access-Control-Expose-Headers: PAYMENT-REQUIRED, PAYMENT-RESPONSE, WWW-Authenticate, Payment-Receipt

# body
{
  "error": {
    "code": "payment_required",
    "message": "This call costs $1.00 USD. Pay inline with x402 (USDC on Base, Polygon or Solana; retry with PAYMENT-SIGNATURE) or, for inbox creation, with Stripe MPP (retry with Authorization: Payment). Or send an API key: Authorization: Bearer dse_...",
    "price_usd": "1.00",
    "docs": "https://deadsimple.email/pay-per-request.html"
  },
  "meta": { "request_id": "..." },
  "x402Version": 2,
  "resource": {
    "url": "https://api.deadsimple.email/v1/inboxes",
    "description": "Dead Simple Email: Create an inbox (returns an API key on first purchase)",
    "mimeType": "application/json"
  },
  "accepts": [
    { "scheme": "exact", "network": "eip155:8453", "amount": "1000000",
      "asset": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913", "payTo": "0x...",
      "maxTimeoutSeconds": 300, "extra": { "name": "USD Coin", "version": "2" } },
    { "scheme": "exact", "network": "eip155:137", "amount": "1000000",
      "asset": "0x3c499c542cEF5E3811e1192ce70d8cC03d5c3359", "payTo": "0x...",
      "maxTimeoutSeconds": 300, "extra": { "name": "USD Coin", "version": "2" } },
    { "scheme": "exact", "network": "solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp", "amount": "1000000",
      "asset": "EPjFWdd5AufqSSqeM2qN1xzybapC8G4wEGGkZwyTDt1v", "payTo": "...",
      "maxTimeoutSeconds": 300, "extra": { "feePayer": "..." } }
  ],
  "extensions": {}
}

# request (v2)
PAYMENT-SIGNATURE: <base64 JSON>
{
  "x402Version": 2,
  "resource": { "url": "https://api.deadsimple.email/v1/inboxes", "...": "..." },
  "accepted": { /* the "accepts" entry you chose, verbatim */ },
  "payload": {
    "signature": "0x...",
    "authorization": { "from": "0xYourWallet", "to": "<payTo>", "value": "1000000",
                      "validAfter": "0", "validBefore": "...", "nonce": "0x..." }
  }
}

# request (v1): the same idea under X-PAYMENT, with "network": "base" and no "accepted"

# response
PAYMENT-RESPONSE: <base64 JSON>
X-PAYMENT-RESPONSE: <same>
{ "success": true, "transaction": "0x9f3c...", "network": "eip155:8453", "payer": "0xYourWallet" }

# a rejected payment is a fresh 402: the requirements are re-emitted and
# error.reason says why (amount mismatch, network not accepted, insufficient_funds, ...)

import { wrapFetchWithPayment } from "@x402/fetch"
import { createWalletClient, http } from "viem"
import { privateKeyToAccount } from "viem/accounts"
import { base } from "viem/chains"

const account = privateKeyToAccount(process.env.AGENT_WALLET_KEY as `0x${string}`)
const wallet = createWalletClient({ account, chain: base, transport: http() })
const fetchWithPay = wrapFetchWithPayment(fetch, wallet)   // pays 402s with USDC on Base

const r = await fetchWithPay("https://api.deadsimple.email/v1/inboxes", {
  method: "POST",
  headers: { "Content-Type": "application/json" },
  body: JSON.stringify({ display_name: "Paid Bot" }),
})
const { data } = await r.json()
console.log(data.email, data.credentials?.api_key)   // store the key; it is shown once

import os, httpx
from eth_account import Account
from x402.clients.httpx import x402_payment_hooks   # the httpx event hooks; see the x402 README

account = Account.from_key(os.environ["AGENT_WALLET_KEY"])

with httpx.Client(base_url="https://api.deadsimple.email") as client:
    client.event_hooks = x402_payment_hooks(account)   # 402 -> sign -> retry, transparently
    r = client.post("/v1/inboxes", json={"display_name": "Paid Bot"})
    data = r.json()["data"]
    print(data["email"], data.get("credentials", {}).get("api_key"))

WWW-Authenticate: Payment id="k9Qw...", realm="api.deadsimple.email", method="stripe", intent="charge",
                  expires="2026-09-11T14:10:00Z", request="eyJhbW91bnQiOiIxMDAiLCJjdXJyZW5jeSI6InVzZCIs..."

# request, decoded
{
  "amount": "100",                       // cents
  "currency": "usd",
  "description": "Dead Simple Email: Create an inbox (returns an API key on first purchase)",
  "methodDetails": { "paymentMethodTypes": ["card", "link"] }
}

# request
Authorization: Payment <base64url JSON>
{
  "challenge": { "id": "k9Qw...", "realm": "api.deadsimple.email", "method": "stripe", "intent": "charge",
                 "expires": "2026-09-11T14:10:00Z", "request": "eyJhbW91bnQiOiIxMDAi..." },
  "payload": { "spt": "spt_..." }
}

# response: 201 with the inbox, credentials and payment {"reference": "pi_...", "method": "stripe"}
Payment-Receipt: <base64url JCS JSON>
{ "amount": "100", "currency": "usd", "method": "stripe", "reference": "pi_...",
  "status": "success", "timestamp": "2026-09-11T14:06:12Z" }

# Stripe Link CLI: fetch the URL, pay the challenge with your Link wallet, print the result
npx @stripe/link-cli mpp pay https://api.deadsimple.email/v1/inboxes

# In code: mppx (npm) or pympp (PyPI) wrap fetch / httpx the same way the x402 clients do.
# The response is the same 201 with credentials.api_key; keep the key for every call after.