# MCPFax Reliability Preflight Check

> MCPFax Reliability Preflight Check is a paid API for AI agents from mcpfax-reliability.bowling-anthony.workers.dev, paid per call via x402, $0.008/call, status unknown (last checked 2026-09-13).

Runs a live preflight probe on a single HTTP/x402 endpoint and returns an ALLOW, WARN, or UNKNOWN advisory based on real-time reachability plus observed reliability history before you make a consequential call.

## Facts

- Endpoint: GET https://mcpfax-reliability.bowling-anthony.workers.dev/preflight
- Price: $0.008/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-13
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/mcpfax-reliability-preflight-check-a48891fd
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_7YerCwS3YOZSILKmxdWbv

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 mcpfax-reliability-preflight-check-a48891fd
```

Example prompt: Before I call that paid MCP endpoint, can you run a preflight reliability check on it — I need to know if it's reachable, what it currently costs, where the payment goes, and whether it's been stable enough that I should trust it with a live request?

## When to prefer this

Use this endpoint when an AI agent is about to make a consequential or paid call to an x402 or MCP endpoint and needs a low-cost advisory signal before committing. It is especially valuable when you want to combine live reachability with observed history (reliability trends, payTo stability, price changes) in a single call. Prefer this over a raw HTTP ping when you want a structured ALLOW/WARN/UNKNOWN verdict rather than just a status code, or when you are onboarding a new vendor endpoint and need trust signals before automating payments.

## Known failure modes

- Target endpoint is unreachable — probe fails with no reachability data, advisory likely UNKNOWN
- No historical observation data available for the target — returns UNKNOWN with live probe only
- Target URL malformed or unsupported type — returns validation error on input
- MCPFax has no prior record of the endpoint — first-seen and reliability fields will be absent
- Probe times out — latency field reflects timeout, advisory may degrade to WARN or UNKNOWN

## How this service works

Advisory preflight on one endpoint before a consequential call: a bounded live probe (reachable, status, latency, MCP initialize, current x402 price and payTo) joined to our observed history (reliability over a stated window, payTo and price changes, first seen). Returns ALLOW, WARN or UNKNOWN. Never a guarantee. No evidence, no charge.

## Output

Returns an advisory verdict of ALLOW, WARN, or UNKNOWN, combined with: live probe results (reachability, HTTP status, latency, MCP initialize handshake), current x402 price and payTo address, and historical signals (reliability score over a stated window, payTo and price change history, first-seen date). No guarantee is implied; no charge is made if no evidence is available.

## 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"
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object"
    }
   }
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/mcpfax-reliability-preflight-check-a48891fd/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from mcpfax-reliability.bowling-anthony.workers.dev](https://www.zero.xyz/host/mcpfax-reliability.bowling-anthony.workers.dev/llms.txt)