# Hello World Greeting (x402 Paid)

> Hello World Greeting (x402 Paid) 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 2026-10-10, last successful call 2026-06-15).

Returns a personalized greeting message including the caller's name and city after verifying a micropayment of $0.001 USDC on Base (eip155:8453).

## Facts

- Endpoint: GET https://hello-world-x402.vercel.app/greet?utm_source=zero.xyz
- Price: $0.001/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-10
- Last successful call: 2026-06-15
- Success rate: 100% of calls made through Zero
- Rating: 5.0 / 5 from 2 reviews
- Activations on Zero: 2
- Tags: x402
- Canonical page: https://www.zero.xyz/c/hello-world-x402-vercel-app-1a773c02
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_8ybWNPs2bSZG3WrjHeE9q

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-1a773c02
```

Example prompt: Get me a personalized greeting for Alex, age 28, living in San Francisco — using the hello-world-x402 greet endpoint that charges a tiny USDC micropayment.

## When to prefer this

Use this endpoint when you want to test or demonstrate x402 micropayment-gated APIs on the Base network, or when you need a simple personalized greeting with a name and city. Ideal for developers evaluating USDC micropayment flows or prototyping paid-API interactions at very low cost ($0.001 per call).

## Known failure modes

- Payment not received or incorrect amount — returns HTTP 402 with payment requirements
- Payment timeout exceeded (300s) — request expires and must be retried
- Missing required query params 'name' or 'city' — returns validation error
- Name exceeds 100 character limit — returns schema validation error
- Age value outside 0-120 range — returns validation error
- Network connectivity issues with Base (eip155:8453) — payment cannot be verified

## How this service works

Returns personalized greeting - UPDATED SCHEMA v2

## Output

A JSON object containing a personalized greeting message (e.g. 'Hello, Alex from San Francisco!'), a timestamp of when the greeting was generated, and a version field — returned after successful $0.001 USDC payment verification on Base.

## 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",
     "required": [
      "name",
      "city"
     ],
     "properties": {
      "age": {
       "type": "number",
       "maximum": 120,
       "minimum": 0,
       "description": "Person's age - UPDATED max to 120"
      },
      "city": {
       "type": "string",
       "maxLength": 100,
       "description": "Person's city - NEW FIELD"
      },
      "name": {
       "type": "string",
       "maxLength": 100,
       "minLength": 1,
       "description": "Person's name - UPDATED"
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object",
     "required": [
      "message",
      "timestamp"
     ],
     "properties": {
      "message": {
       "type": "string"
      },
      "version": {
       "type": "string"
      },
      "timestamp": {
       "type": "string"
      }
     }
    }
   }
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/hello-world-x402-vercel-app-1a773c02/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)