# hello-world-x402 /world - Reverse Greeting Endpoint

> hello-world-x402 /world - Reverse Greeting 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 2026-10-22).

Returns the string 'World Hello' (a reversed greeting) as a plain-text response after micropayment verification via x402

## Facts

- Endpoint: GET https://hello-world-x402.vercel.app/world?utm_source=zero.xyz
- Price: $0.001/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-22
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/hello-world-x402-vercel-app-720597b0
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap__ukOX_RrVQnOPFi7wsVBw

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-720597b0
```

Example prompt: Fetch the reversed greeting from the hello-world-x402 /world endpoint — it should return 'World Hello' as plain text after the $0.001 USDC micropayment goes through.

## When to prefer this

Use this endpoint when you need to test or demonstrate the x402 micropayment protocol with a minimal, predictable plain-text response. It is ideal for verifying that a $0.001 USDC pay-per-call flow works end-to-end, or for integration testing of x402-enabled agent payment pipelines. Not suitable for production use cases requiring meaningful data.

## Known failure modes

- Payment not provided or incorrect amount: 402 Payment Required response with payment details
- Network or Vercel deployment unavailable: 503 or timeout
- Invalid HTTP method (non-GET): 405 Method Not Allowed
- Payment verification failure on eip155:845 network: payment rejected or unconfirmed

## How this service works

Returns "World Hello" - UPDATED TEST v2.0

## Output

A plain-text string 'World Hello' returned with content-type text/plain; charset=utf-8. This is a simple reversed greeting used to demonstrate and test x402 pay-per-call functionality.

## Example request

```json
{
 "input": {
  "type": "http",
  "method": "GET",
  "queryParams": {}
 }
}
```

## 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 greeting message in reverse - UPDATED FOR TESTING PROPAGATION"
    }
   }
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/hello-world-x402-vercel-app-720597b0/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)