# aeml-x402 Tier 3 Payment Receipt

> aeml-x402 Tier 3 Payment Receipt is a paid API for AI agents from aeml-x402.zeabur.app, paid per call via x402, $0.1/call, status unknown (last checked 2026-09-14).

Issues a short-lived signed payment receipt for tier 3 access after processing a $0.10 USDC x402 payment on Base, verifiable via /pay/verify.

## Facts

- Endpoint: GET https://aeml-x402.zeabur.app/pay/tier3
- Price: $0.1/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/aeml-x402-tier-3-payment-receipt-12d97fba
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_oOnzjdnKHKguLUPhfO3GU

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 aeml-x402-tier-3-payment-receipt-12d97fba
```

Example prompt: Pay $0.10 USDC via x402 on Base to get a signed tier 3 access receipt I can use to verify my payment with the gauge-frontdesk service.

## When to prefer this

Use this endpoint when you need tier 3 (highest) access level to the aeml-x402 service and want to pay via x402 USDC micropayment on Base. Prefer this over tier 1 or tier 2 endpoints when the downstream resource requires tier 3 authorization. It is the right choice for agents that need to programmatically acquire short-lived signed credentials tied to a crypto micropayment rather than API key-based auth.

## Known failure modes

- Payment not included or malformed x402 header — returns 402 Payment Required
- Payment amount insufficient for tier 3 — payment rejected
- Receipt already expired — must re-pay to get a fresh receipt
- Invalid or missing ref hash format — may return error or null ref
- Network or provider outage on Base — payment processing fails

## How this service works

Tiered payment receipt (tier 3): pay once with x402 and get back a short-lived receipt token that /pay/verify checks for you. The tier is fixed by the path - you do not send it. Optional ?ref= carries your own opaque reference, such as a query hash, straight through to the receipt. This mints a receipt rather than returning data, so there is no lookup that can come back empty.

## Output

Returns a JSON object with: ok (boolean success), receipt (short-lived signed receipt string), exp (Unix expiry timestamp), tier (integer, value 3), paid_via (payment method string, e.g. x402/USDC/Base), and optional ref (query hash if supplied). The receipt can be passed to /pay/verify for downstream authorization checks.

## Request schema (JSON Schema)

```json
{
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "properties": {
  "input": {
   "type": "object",
   "properties": {
    "type": {
     "const": "http"
    },
    "method": {
     "type": "string",
     "enum": [
      "GET"
     ]
    },
    "queryParams": {
     "type": "object",
     "additionalProperties": false,
     "properties": {
      "tier": {
       "type": "string",
       "description": "optional - ignored; fixed to 3 by this path"
      },
      "ref": {
       "type": "string",
       "description": "optional - opaque reference such as a query hash"
      }
     }
    }
   },
   "required": [
    "type",
    "method"
   ]
  },
  "output": {
   "type": "object",
   "properties": {
    "type": {
     "const": "json"
    }
   },
   "required": [
    "type"
   ]
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json"
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/aeml-x402-tier-3-payment-receipt-12d97fba/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from aeml-x402.zeabur.app](https://www.zero.xyz/host/aeml-x402.zeabur.app/llms.txt)