{"uid":"cap_P8HgZs1-Sn45N_0hw0Saj","slug":"mailpulse-physical-letter-sender-a6271e2c","name":"MailPulse Physical Letter Sender","description":"MailPulse sends REAL physical letters — US First-Class, US Certified Mail, or international — via x402 micropayments. Action, not data: free quote, paid send, optional tracking. Powered by Lob.","url":"https://mailpulse.theaslangroupllc.com/api/letters","method":"POST","headers":{},"bodySchema":{"type":"object","required":["to","from","content","service","quote_id","issued_at","amount_micro","client_request_id"],"properties":{"to":{"type":"object","description":"Recipient address"},"from":{"type":"object","description":"Sender-of-record address (never us)"},"content":{"type":"object","description":"{ html } or { file_url }"},"service":{"type":"string","description":"standard | certified | certified_return_receipt | international"},"quote_id":{"type":"string","description":"From POST /api/quote"},"issued_at":{"type":"string","description":"From POST /api/quote, copied verbatim"},"amount_micro":{"type":"string","description":"From POST /api/quote, copied verbatim"},"client_request_id":{"type":"string","description":"8-128 chars, unique per letter, enables idempotent retries"}}},"responseSchema":{"type":"json","example":{"id":"ltr_...","mode":"test","status":"processed","carrier":"USPS","service":"standard","tracking_number":null,"price_charged_usd":"3.00","expected_delivery_date":"2026-07-23"}},"example":null,"exampleRequest":null,"tags":["x402"],"displayCostAmount":"7.005","displayCostAsset":"USDC","priceDynamic":false,"priceHint":null,"priceStatus":"priced","priceSource":"settled","requiresHandshake":false,"reviewCount":1,"rating":{"score":"0.83","successRate":"0.86","reviews":1,"stars":"4.3","state":"rated"},"availabilityStatus":"healthy","priceObserved":{"p10Cents":"1.0000","medianCents":"700.5000","p90Cents":"1400.0000","minCents":"1.0000","maxCents":"1400.0000","p95Cents":"1400.0000","sampleCount":4,"varies":false,"failureChargeRate":null},"sessionDeposit":null,"pricing":{"kind":"static","summary":"$7.005/call","primary":{"kind":"static","protocol":"x402","network":"base","amountUsd":"3","per":"call","confidence":"exact"},"accepted":[{"kind":"static","protocol":"x402","network":"base","amountUsd":"3","per":"call","confidence":"exact"}]},"paymentMethods":[{"uid":"pm_UO8e81vQDmLU0dUQv40iL","protocol":"x402","methodType":"crypto","chain":"base","mode":"charge","costAmount":"3","costPer":"request","priority":0,"asset":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","unit":"request","depositMicros":null,"planRef":null}],"brandName":null,"brandSlug":null,"brandBaseUrl":null,"brandDocsUrl":null,"whatItDoes":"Sends a real physical letter (US First-Class, US Certified Mail, or international) via USPS using a pre-obtained quote ID, paid via x402 micropayment","exampleAgentPrompt":"Send a first-class physical letter to John Smith at 123 Main St, Springfield, IL 62701 from Acme Corp at 456 Oak Ave, Chicago, IL 60601 — the content is an HTML invoice I have ready, and use the quote I just got (quote ID q_abc123).","exampleUseCases":[{"title":"Automated legal notice mailing","prompt":"Mail a certified letter with return receipt to my tenant Maria Gonzalez at 789 Elm Street, Austin TX 78701 from my property management company at 100 Commerce Blvd, Austin TX 78702 — the content is an HTML eviction notice I have prepared. Use the certified_return_receipt service and the quote ID I got earlier."},{"title":"Customer invoice by post","prompt":"Send a first-class letter to our customer Robert Chen at 55 Park Avenue, New York NY 10016 from Brightline Billing at 200 Wall St, New York NY 10005 with this month's invoice as an HTML file. It's a standard domestic letter — use the quote ID q_inv_2024_06."},{"title":"International business correspondence","prompt":"Mail an international letter to Sophie Dupont at 12 Rue de Rivoli, Paris 75001, France from Global Ventures LLC at 300 Mission St, San Francisco CA 94105 — the content is a partnership agreement in HTML. Use the international service and quote ID q_intl_8821."}],"resultDescription":"A JSON object containing the letter's unique ID (ltr_...), its processing status, the carrier (USPS), service level used, a tracking number if applicable (null for standard), the USD price charged, and the expected delivery date.","failureModes":["Expired or mismatched quote_id — quote must be obtained fresh from /api/quote and used promptly","Invalid or undeliverable recipient/sender address — use the address verification endpoint first","Malformed HTML or inaccessible file_url in content field","Duplicate client_request_id for a different letter — must be unique per send","Insufficient x402 payment or payment verification failure","International address format errors or unsupported destination country"],"whenToPreferThis":"Choose this endpoint when you need to physically mail an actual letter via USPS — not an email, not a digital document, but a real envelope delivered to a real address. It is ideal for legal notices, certified mail with tracking, customer correspondence, or any workflow where a physical paper trail is required. It is backed by Lob for reliable USPS integration and supports certified and international mail that other digital-only services cannot provide.","instructions":null,"reviewSummary":null,"reviewSummaryHighlights":null,"reviewSummaryConcerns":null,"reviewSummaryGeneratedAt":null,"activationCount":8,"lastUsedAt":"2026-09-12T15:50:43.813Z","lastSuccessfullyRanAt":"2026-09-12T15:50:43.813Z","lastHealthCheckAt":"2026-09-15T11:00:03.067Z","isFirstParty":false}