# MailPulse Physical Letter Sender

> MailPulse Physical Letter Sender is a paid API for AI agents from mailpulse.theaslangroupllc.com, paid per call via x402, $7.005/call, status healthy (last checked 2026-09-14, last successful call 2026-09-12).

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

## Facts

- Endpoint: POST https://mailpulse.theaslangroupllc.com/api/letters
- Price: $7.005/call
- Payment: x402
- Status: healthy
- Last checked: 2026-09-14
- Last successful call: 2026-09-12
- Success rate: 86% of calls made through Zero
- Rating: 4.3 / 5 from 1 review
- Activations on Zero: 8
- Tags: x402
- Canonical page: https://www.zero.xyz/c/mailpulse-physical-letter-sender-a6271e2c
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_P8HgZs1-Sn45N_0hw0Saj

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability mailpulse-physical-letter-sender-a6271e2c -d '<json body>'
```

Example prompt: 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).

## When to prefer this

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.

## Known failure modes

- 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

## How this service works

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.

## Output

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.

## Request schema (JSON Schema)

```json
{
 "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"
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "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"
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/mailpulse-physical-letter-sender-a6271e2c/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from mailpulse.theaslangroupllc.com](https://www.zero.xyz/host/mailpulse.theaslangroupllc.com/llms.txt)