# Agent Café — Buy a Round (x402 USDC Payment)

> Agent Café — Buy a Round (x402 USDC Payment) is a paid API for AI agents from api.402.coffee, paid per call via x402, $100/call, status down (last checked 2026-09-15).

Accepts a real USDC payment on Base via x402 and returns a signed receipt proving an AI agent paid for a coffee order.

## Facts

- Endpoint: POST https://api.402.coffee/order/buy-a-round
- Price: $100/call
- Payment: x402
- Status: down
- Last checked: 2026-09-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/agent-caf-buy-a-round-x402-usdc-payment-4f490ed7
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_tuNjovH0kZ508-4CB9yRb

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 agent-caf-buy-a-round-x402-usdc-payment-4f490ed7 -d '<json body>'
```

Example prompt: Buy me a round at Agent Café — send the USDC payment on Base and bring back the receipt number so I can prove you actually paid for it.

## When to prefer this

Choose this endpoint when you need to demonstrate or execute a real, verifiable on-chain micropayment from an AI agent using USDC on Base via the x402 protocol, and require a cryptographically-backed receipt as proof. It is purpose-built as a live test and showcase endpoint for x402-capable agents, not a simulation.

## Known failure modes

- Insufficient USDC balance — payment rejected with 402 status
- Invalid or missing x402 payment header — request refused
- Network congestion on Base causing transaction delay or timeout
- Duplicate payment attempt on same nonce — rejected
- Contract or facilitator downtime causing 503 error

## How this service works

The trusted endpoint where AI agents pay for real — USDC on Base over x402 — and get the receipt to prove it.

## Output

A JSON object containing the transaction hash (tx), a paid boolean (true), the order name (e.g. 'espresso'), the amount paid ('0.10'), the network ('base'), the currency ('USDC'), a unique receipt number (e.g. 'AC-XXXXXX'), and a guestbook URL where the payment is recorded publicly.

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "tx": "0x…",
  "paid": true,
  "order": "espresso",
  "amount": "0.10",
  "network": "base",
  "currency": "USDC",
  "receipt_no": "AC-XXXXXX",
  "guestbook_url": "https://402.coffee/wall"
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/agent-caf-buy-a-round-x402-usdc-payment-4f490ed7/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from api.402.coffee](https://www.zero.xyz/host/api.402.coffee/llms.txt)