# numberintel.dev x402 Preflight Attestation

> numberintel.dev x402 Preflight Attestation is a paid API for AI agents from numberintel.dev, paid per call via x402, $0.02/call, status unknown (last checked 2026-10-02).

Checks whether a target x402-enabled HTTP endpoint is reachable, properly configured, and returns a quote for its payment requirements before committing to a paid call.

## Facts

- Endpoint: GET https://numberintel.dev/v1/attest/preflight?utm_source=zero.xyz
- Price: $0.02/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-02
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/numberintel-dev-x402-preflight-attestation-e8f0e039
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_l701tjUXgvcEhBE8QVdP6

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 numberintel-dev-x402-preflight-attestation-e8f0e039
```

Example prompt: Before I call that paid API, can you preflight check https://api.example.com/v1/data to confirm it's reachable, returning a 402 with a valid x402 quote, and tell me how much it costs and what address to pay?

## When to prefer this

Use this endpoint when you need to validate or audit an x402-gated API before making a live paid call — especially to confirm price, payment address, network, and x402 protocol version without spending funds. Prefer it over blindly calling a pay-per-use endpoint when you want to surface configuration problems, confirm Bazaar extension support, or let a user review costs before authorizing payment.

## Known failure modes

- Target URL unreachable — reachable: false with empty quote and non-empty problems list
- Target does not return HTTP 402 — grade reflects non-conformant status
- Malformed x402 response at target — problems list populated with parse errors
- Missing required query parameter 'target' — 400 Bad Request
- Payment not settled for this preflight call itself — 402 returned by the preflight endpoint
- Network timeout on target URL — reachable: false

## How this service works

x402 conformance preflight of any endpoint: parses the 402 envelope, lints accepts[] (atomic units, payTo, network), reports the quote, Bazaar extension presence and problems. No purchase is made.

## Output

Returns a JSON object with a grade (e.g. 'quote_ok'), the payment quote including USD price, payTo address, and network, whether the endpoint is reachable, the HTTP status code, x402 version, number of accepted payment options, whether a Base mainnet option exists, whether the Bazaar extension is present, and a list of any detected problems.

## 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": [
      "target"
     ],
     "properties": {
      "method": {
       "type": "string",
       "description": "GET or POST, default GET"
      },
      "target": {
       "type": "string",
       "description": "https URL of the x402 endpoint to check"
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object"
    }
   }
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "grade": "quote_ok",
  "quote": {
   "usd": 0.01,
   "payTo": "0x...",
   "network": "eip155:8453"
  },
  "target": "https://api.example.com/v1/data",
  "problems": [],
  "reachable": true,
  "http_status": 402,
  "x402_version": 2,
  "accepts_count": 1,
  "base_mainnet_option": true,
  "has_bazaar_extension": true
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/numberintel-dev-x402-preflight-attestation-e8f0e039/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from numberintel.dev](https://www.zero.xyz/host/numberintel.dev/llms.txt)