# Hello World x402 Demo Endpoint

> Hello World x402 Demo Endpoint is a paid API for AI agents from hello-world-x402.vercel.app, paid per call via x402, $0.001/call, status unknown (last checked 2026-09-15).

Returns a simple 'Hello World' string after verifying a $0.001 USDC micropayment via the x402 payment protocol

## Facts

- Endpoint: GET https://hello-world-x402.vercel.app/hello
- Price: $0.001/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/hello-world-x402-vercel-app-d23d4494
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_aOH3VmldxiZY242FO0mdk

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 hello-world-x402-vercel-app-d23d4494
```

Example prompt: Can you call the hello-world x402 demo endpoint to test that micropayments are working — it should return 'Hello World' after the $0.001 USDC payment goes through?

## When to prefer this

Use this endpoint when you want to test or demonstrate the x402 micropayment protocol in action, verify that a USDC-gated HTTP call works end-to-end, or confirm your x402 client implementation is functioning correctly. It is a canonical 'hello world' demo of pay-per-call APIs and is ideal for integration smoke tests.

## Known failure modes

- Payment not included or malformed x402 header — returns HTTP 402 Payment Required
- Insufficient USDC balance — payment verification fails
- Network mismatch (wrong chain, not eip155:8453/Base) — payment rejected
- Invalid or expired payment — returns authorization error
- Rate limiting or Vercel deployment unavailability — returns 5xx error

## How this service works

Returns "Hello World" after payment verification

## Output

A simple greeting string 'Hello World' returned after successful x402 payment verification, confirming the micropayment flow completed successfully.

## 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": [
      "GET"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "properties": {}
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "string",
     "description": "A simple greeting message"
    }
   }
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/hello-world-x402-vercel-app-d23d4494/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from hello-world-x402.vercel.app](https://www.zero.xyz/host/hello-world-x402.vercel.app/llms.txt)