# x402 Doctor – Deep Preflight Check

> x402 Doctor – Deep Preflight Check is a paid API for AI agents from x402-doctor.fizzl.eu, paid per call via x402, $0.01/call, status unknown (last checked 2026-10-11).

Performs a comprehensive pre-payment analysis of an x402 endpoint, returning a pay/no-pay verdict, 30-day reliability history, seller reputation across endpoints, domain stability checks, and full diagnostics — without ever paying the endpoint.

## Facts

- Endpoint: GET https://x402-doctor.fizzl.eu/api/v1/preflight/deep?utm_source=zero.xyz
- Price: $0.01/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-11
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/x402-doctor-deep-preflight-check-e391023d
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_HdAs3hWCF_t87DB382ZoS

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-doctor-deep-preflight-check-e391023d
```

Example prompt: Before you pay for that x402 endpoint at https://api.example.com/data, run a deep preflight check on it with a budget cap of $0.05 per call on Ethereum mainnet and tell me whether it's safe to pay, what its 30-day history looks like, and how reliable the seller's other endpoints are.

## When to prefer this

Use this endpoint when your agent is about to pay an x402 endpoint that is expensive (e.g. >$0.01), unfamiliar, or mission-critical, and you want a full deep analysis including 30-day history, seller reputation across all their endpoints, and domain movement checks. Prefer it over the lightweight single-check endpoint when you need the historical trend data and seller-level trust signals, not just a one-shot verdict. Choose it over the batch endpoint when you need the richest possible data on a single URL rather than quick verdicts across many URLs.

## Known failure modes

- Target URL is unreachable — verdict returns 'unreachable' status with no payment options
- URL parameter missing or malformed — API returns validation error
- Endpoint is not an x402 endpoint — diagnosis returns unknown status with explanation
- Budget (max_usd) is below all available payment options — verdict is forced no_go
- Network CAIP-2 identifier is invalid — API returns parameter error
- Target endpoint has no history yet — history array returns empty or unknown entries

## How this service works

Should my agent pay this expensive x402 endpoint? Call it before a costly or repeated payment. Returns the go / caution / no_go verdict plus the full diagnosis, the endpoint's check history per day over 30 days, how reliable the seller's other endpoints are and whether the endpoint moved domains. Never pays the endpoint. Bulk: 1000 credits for $0.80 via /api/v1/credits.

## Output

Returns a structured verdict object including: a top-level verdict (go/caution/no_go), a safe_to_pay boolean, a human-readable summary, an array of per-payment-option details (network, asset, USD price, payability problems), a list of reasons driving the verdict, a 30-day daily history of endpoint status, seller statistics (total resources, unreliable count, payable ratio), domain stability checks, and a cached flag indicating whether the result was served from cache.

## 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": [
      "url"
     ],
     "properties": {
      "url": {
       "type": "string",
       "description": "The x402 endpoint you are about to pay (worth it for expensive calls)."
      },
      "method": {
       "enum": [
        "GET",
        "POST"
       ],
       "type": "string",
       "description": "HTTP method you will call it with. Default: try GET, then POST."
      },
      "max_usd": {
       "type": "string",
       "description": "Your budget per call in USD; above it the verdict is no_go."
      },
      "network": {
       "type": "string",
       "description": "CAIP-2 network you want to pay on."
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object",
     "required": [
      "url",
      "verdict",
      "safe_to_pay",
      "summary",
      "options",
      "reasons"
     ],
     "properties": {
      "url": {
       "type": "string"
      },
      "cached": {
       "type": "boolean"
      },
      "domain": {
       "type": "object",
       "properties": {
        "checks": {
         "type": "array"
        }
       }
      },
      "method": {
       "type": [
        "string",
        "null"
       ]
      },
      "seller": {
       "type": [
        "object",
        "null"
       ],
       "properties": {
        "origin": {
         "type": "string"
        },
        "resources": {
         "type": "integer"
        },
        "unreliable": {
         "type": "integer"
        },
        "payable_now": {
         "type": "integer"
        },
        "avg_payable_ratio": {
         "type": "number"
        }
       }
      },
      "history": {
       "type": "array",
       "items": {
        "type": "object",
        "properties": {
         "date": {
          "type": [
           "string",
           "null"
          ]
         },
         "status": {
          "enum": [
           "go",
           "caution",
          
… (truncated)
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/x402-doctor-deep-preflight-check-e391023d/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from x402-doctor.fizzl.eu](https://www.zero.xyz/host/x402-doctor.fizzl.eu/llms.txt)