Machine Inbox buyer examples

The live service sells on two payment rails. Stripe Machine Payments
Protocol (MPP): $2.00 USD for a seven-day inbox, $5.00 for a thirty-day pro
inbox (500 messages, 100 MiB, 50 replies per day), and $1.00 to extend an
active inbox seven more days. x402 v2 (USDC on Base mainnet, settled through
the PayAI facilitator): the same three products; the pro tier sells over
x402 at its own path, POST /api/v1/inboxes/pro. Every purchase includes
authenticated replies under the published limits.

Stripe Link CLI

  npx @stripe/link-cli mpp pay https://machineinbox.com/api/v1/inboxes \
    --context "Create one seven-day Machine Inbox for an automated task"

The client handles the HTTP 402 WWW-Authenticate challenge, obtains a Stripe
Shared Payment Token, retries with Authorization: Payment, and prints the
successful response. That response contains the inbox ID, address, expiry,
and mailbox bearer token. Store the token as a secret.

x402

  X402_PRIVATE_KEY=0x... bun run create-inbox-x402.ts

The same unpaid 402 also carries a base64 PAYMENT-REQUIRED header with an
x402 v2 requirement. An x402 client signs USDC on Base mainnet and retries
with PAYMENT-SIGNATURE. x402 purchases require an Idempotency-Key.

For reliable application retries on either rail, send a unique
Idempotency-Key on the initial request and reuse it on the paid retry. The
official `mppx validate` command can call this endpoint without that
application-specific header; Machine Inbox binds a generated key into the
MPP challenge in that case.

Files in this directory

  create-inbox.ts        Buy an inbox with the Stripe Link CLI
  create_inbox.py        The same Stripe MPP purchase from Python
  create-inbox-x402.ts   Buy an inbox with x402: USDC on Base mainnet
  raw-402-flow.txt       The exact Stripe MPP 402 challenge and paid retry
  raw-402-flow-x402.txt  The exact x402 402 challenge and paid retry
  read-reply-loop.ts     Post-purchase loop: list, read, reply, poll delivery
  read_reply_loop.py     The same post-purchase loop from Python
  extend-inbox.ts        Extend an active inbox by seven days for $1.00

After purchase, on either rail: poll GET /api/v1/inboxes/{id}/messages with
after=<newest createdAt seen>, and use GET
/api/v1/inboxes/{id}/verification-code to extract one-time codes from signup
mail without MIME parsing. An MCP server for the post-purchase surface is at
https://machineinbox.com/mcp.

Validation

  npx mppx@latest validate https://machineinbox.com

The Stripe MPP guide is at https://docs.stripe.com/payments/machine/mpp
The x402 spec is at https://www.x402.org