# x402 Alert Username Check API

> x402 Alert Username Check API is a paid API for AI agents from x402-alert.vercel.app, paid per call via x402, $0.05/call, status unknown (last checked 2026-09-15).

Checks the availability or validity of a username, paid via USDC on Base using the x402 protocol

## Facts

- Endpoint: POST https://x402-alert.vercel.app/api/username-check
- Price: $0.05/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/x402-alert-username-check-api-51709f2a
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_9QRtYsHO1kjRkBJxjDZ6C

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 x402-alert-username-check-api-51709f2a -d '<json body>'
```

Example prompt: Can you check if the username 'cryptowatcher99' is available using the x402 Alert API? I'm okay paying the small USDC fee.

## When to prefer this

Use this endpoint when you need to programmatically verify whether a specific username is available or valid and are comfortable paying micro-transactions in USDC on the Base network via the x402 protocol. Prefer this over free alternatives when integrating with the x402 Alert financial monitoring ecosystem.

## Known failure modes

- Missing or invalid username input returns an error
- Insufficient USDC balance for x402 payment causes payment failure
- Network error on Base blockchain during payment processing
- Malformed request body results in 400 Bad Request
- Username field empty or null causes validation error

## How this service works

14 paid financial API endpoints. Pay with USDC on Base using x402 protocol.

## Output

Returns a result object containing data about the username check, such as whether the username is available, taken, or valid, along with any relevant metadata returned by the API.

## Response schema (JSON Schema)

```json
{
 "type": "object",
 "example": {
  "result": {
   "data": "example response"
  }
 },
 "properties": {
  "result": {
   "type": "object",
   "description": "API response data"
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/x402-alert-username-check-api-51709f2a/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from x402-alert.vercel.app](https://www.zero.xyz/host/x402-alert.vercel.app/llms.txt)