# x402 Field Instruments – Source Proof

> x402 Field Instruments – Source Proof is a paid API for AI agents from bj7e26lfpo4fthvr35hczdipby.srv.us, paid per call via x402, $0.002/call, status unknown (last checked 2026-09-14).

Fetches a public HTTPS URL and returns a cryptographic SHA-256 proof of its content, byte count, final URL, and HTTP status at a given moment.

## Facts

- Endpoint: GET https://bj7e26lfpo4fthvr35hczdipby.srv.us/v1/source-proof
- Price: $0.002/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/x402-field-instruments-source-proof-25ce6560
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_XW78SJLuOD-xAAGqRzN-M

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-field-instruments-source-proof-25ce6560
```

Example prompt: Can you fetch https://example.com/report.pdf and give me a SHA-256 proof of exactly what it contains right now, along with the byte count and final URL?

## When to prefer this

Choose this endpoint when you need a cryptographically verifiable, timestamped record of what a public URL served at a specific moment — especially for source integrity auditing, tamper detection, or provenance documentation. It is account-free and pay-per-call at $0.002 USDC, making it ideal for on-demand spot checks without subscription overhead. Prefer it over a plain HTTP fetch when you need the SHA-256 digest and observation timestamp as structured proof artifacts, not just the raw content.

## Known failure modes

- URL is not publicly accessible or returns a non-2xx status — httpStatus field reflects the error code
- URL uses HTTP instead of HTTPS — rejected by schema validation
- Provided expected_sha256 does not match actual content — mismatch surfaced in response
- Network timeout or DNS failure for the target URL — error response returned
- Malformed or non-64-character expected_sha256 pattern — schema validation error before call

## How this service works

Seven account-free paid tools for source integrity, x402 catalog search, preflight, liveness, routing, price drift, and batch verification.

## Output

A JSON object containing: the 64-character SHA-256 digest of the fetched content, total byte count, the final resolved URL (after any redirects), the HTTP status code, the ISO-8601 timestamp of observation, and a proof version string. Together these fields constitute a verifiable, timestamped fingerprint of the resource.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "required": [
      "url"
     ],
     "properties": {
      "url": {
       "type": "string",
       "description": "Public HTTPS URL to inspect"
      },
      "expected_sha256": {
       "type": "string",
       "pattern": "^[A-Fa-f0-9]{64}$"
      }
     },
     "additionalProperties": false
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object"
    }
   }
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "bytes": 1256,
  "sha256": "64-character SHA-256 digest",
  "finalUrl": "https://example.com/robots.txt",
  "httpStatus": 200,
  "observedAt": "2026-08-27T00:00:00.000Z",
  "proofVersion": "1.0"
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/x402-field-instruments-source-proof-25ce6560/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from bj7e26lfpo4fthvr35hczdipby.srv.us](https://www.zero.xyz/host/bj7e26lfpo4fthvr35hczdipby.srv.us/llms.txt)