# PostAgent Physical Mail API – Print & Mail Letter via USPS

> PostAgent Physical Mail API – Print & Mail Letter via USPS is a paid API for AI agents from postagent-api.interpretai.tech, paid per call via x402, $1.37/call, status unknown (last checked 2026-09-15).

Prints and mails a physical US letter (PDF, HTML, Markdown, DOCX, or image) via USPS, paid in USDC using the x402 payment protocol

## Facts

- Endpoint: POST https://postagent-api.interpretai.tech/v1/print
- Price: $1.37/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/postagent-physical-mail-api-print-mail-letter-via-usps-a6355ee7
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_fW4CWP3HAo3ZueqbeCUWj

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 postagent-physical-mail-api-print-mail-letter-via-usps-a6355ee7 -d '<json body>'
```

Example prompt: Mail this attached PDF contract to John Smith at 123 Main St, Austin TX 78701 — print it and send it via USPS, and notify me at https://myapp.com/webhooks/mail when it's been dispatched.

## When to prefer this

Use this endpoint when an AI agent needs to physically mail a document to a US address via USPS, especially in automated workflows where the user cannot or does not want to visit a post office. Ideal for sending invoices, legal notices, contracts, or personal letters in digital formats (PDF, HTML, Markdown, DOCX, image). Prefer this over email delivery when a physical paper record is required or when the recipient does not have a digital address. The USDC/x402 payment model makes it suitable for crypto-native or agent-driven workflows without traditional billing setup.

## Known failure modes

- Invalid or unsupported document format — only PDF, HTML, Markdown, DOCX, and image files are accepted
- Missing required quote step — the x402 payment URL must be obtained from /v1/quotes before calling /v1/print
- Payment failure — insufficient USDC balance or invalid x402 payment header
- Invalid US recipient address — non-US or malformed addresses will be rejected
- Webhook URL unreachable — optional webhook notifications may silently fail if the provided URL is unavailable
- Document upload not completed — /v1/documents must be called first to upload the file before printing

## How this service works

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.

## Output

The agent receives confirmation that the letter has been created and queued for USPS mailing, along with a job ID and status. If a webhookUrl was provided, the agent also receives asynchronous status updates (e.g. created, mailed) posted to that URL. The fixed USDC price was locked at the quote stage before this call.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "POST"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "properties": {
      "webhookUrl": {
       "type": "string",
       "description": "Optional HTTPS URL that receives job status webhooks after the letter is created."
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object"
    }
   }
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/postagent-physical-mail-api-print-mail-letter-via-usps-a6355ee7/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from postagent-api.interpretai.tech](https://www.zero.xyz/host/postagent-api.interpretai.tech/llms.txt)