# 100BTC x402 Challenge Check

> 100BTC x402 Challenge Check is a paid API for AI agents from vps-fc89c157-1.taila28d02.ts.net:10000, paid per call via x402, $0.005/call, status unknown (last checked 2026-09-30).

Validates the structural correctness of an x402 v2 payment challenge object against the declared spec without performing any remote fetch, settlement, or on-chain verification.

## Facts

- Endpoint: POST https://vps-fc89c157-1.taila28d02.ts.net:10000/api/x402-challenge-check?utm_source=zero.xyz
- Price: $0.005/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-30
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/100btc-x402-challenge-check-82de6b11
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_fnFcmk6xlZPz4LCB1pMn1

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 100btc-x402-challenge-check-82de6b11 -d '<json body>'
```

Example prompt: Can you check whether this x402 v2 challenge object is structurally valid — it has x402Version set to 2, a resource URL, and an accepts array — and tell me which fields pass or fail?

## When to prefer this

Choose this endpoint when you need a fast, stateless structural lint of an x402 v2 challenge object before deploying or sending it — especially useful during development, CI pipelines, or debugging rejected 402 flows. It does not verify payments on-chain or settle transactions, so use it only for schema/format validation, not for confirming actual payment receipt.

## Known failure modes

- Missing required fields (x402Version, resource, or accepts) returns valid:false with per-field failures in the checks map
- Wrong x402Version value (not 2) causes x402_version check to fail
- Malformed challenge object structure returns a validation error response
- Server unreachable on the Tailscale VPS address returns a network/connection error
- Incorrect Content-Type or missing request body returns a 400-level parse error

## How this service works

Thirty x402 v2 pay-per-call APIs by 100BTC. Listing data is generated from each live HTTP 402 challenge and runtime Bazaar schema.

## Output

A JSON object containing a top-level 'valid' boolean, a 'status' string (e.g. 'VALID'), a 'checks' map with per-field pass/fail details and human-readable detail strings, a 'scope' disclaimer clarifying no remote or on-chain checks are performed, and a 'product' identifier (e.g. 'EXP-21').

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "challenge": {
   "type": "object",
   "required": [
    "x402Version",
    "resource",
    "accepts"
   ]
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "scope": "declared structure only; no remote fetch, verify, settlement, or on-chain check",
  "valid": true,
  "checks": {
   "x402_version": {
    "detail": "x402Version must be 2",
    "passed": true
   }
  },
  "status": "VALID",
  "product": "EXP-21"
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/100btc-x402-challenge-check-82de6b11/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from vps-fc89c157-1.taila28d02.ts.net:10000](https://www.zero.xyz/host/vps-fc89c157-1.taila28d02.ts.net%3A10000/llms.txt)