Print and mail physical US letters (PDF, HTML, Markdown, DOCX, or image) and postcards via USPS, paid in USDC — with certified/registered proof options and standalone address verification at POST /v1/verify. Integration flow: POST /v1/documents to upload, POST /v1/quotes to lock a fixed USDC price for a recipient, then pay the returned per-quote x402 URL to create and mail the piece. Price is fixed per quote.

Verify a postal address for deliverability, paid in USDC. POST a JSON body { "address": { "line1", "city", "state", "zip", "country?" } } with an X-PAYMENT header to get CASS-standardized deliverability (US) or international verification (2-letter non-US country code). Flat price per call; the same request without a payment header returns the 402 challenge.