# FactStamp Bulk Verification

> FactStamp Bulk Verification is a paid API for AI agents from factstamp.agentrails.workers.dev, paid per call via x402, $0.12/call, status unknown (last checked 2026-10-16).

Verify up to 12 citations or dependency packages in a single batch call at $0.12 flat, returning a verdict for each item.

## Facts

- Endpoint: POST https://factstamp.agentrails.workers.dev/bulk?utm_source=zero.xyz
- Price: $0.12/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-16
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/factstamp-bulk-verification-a9551a3e
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_6kV1k8BdyTgRoft7rVq-J

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 factstamp-bulk-verification-a9551a3e -d '<json body>'
```

Example prompt: Can you bulk-verify these 8 citations for me — DOIs 10.1038/nature12373, 10.1016/j.cell.2021.05.001, and six more from my bibliography — and tell me which ones are verified, retracted, or unreadable before I submit the paper?

## When to prefer this

Use this endpoint when you need to verify multiple citations or packages in a single round trip rather than making individual calls — it costs half as much per item ($0.01 vs $0.02) and guarantees consistent verdicts across all items since they all go through the same verification logic. Prefer it when processing a bibliography, reference list, or dependency manifest of up to 12 items. For ongoing monitoring of a list, consider the standing re-check (watch) endpoint instead.

## Known failure modes

- Exceeds 12-item limit per call — request rejected
- Invalid or malformed DOI/arXiv ID — item returned as unreadable
- Payment settlement failure — call not processed
- Identifier type not supported — verdict may be unreadable
- Network timeout on upstream registry lookups — partial results or error

## How this service works

Check a whole bibliography or dependency manifest in one round trip, before you rely on the list: up to 12 items at a flat US$0.12 — 1 cent an item, against 2 cents for the same lookups one at a time. Every item is answered by the same door that answers a single call, so the verdicts cannot disagree. Pay per call here, or redeem a prepaid pack code (one answer-pack credit per three items, up to 25 items on that rail).

## Output

A JSON object with: total items count, per-item results array (each with tool name, input identifier, and verdict such as 'verified', 'retracted', or 'unreadable'), aggregate by-verdict counts, number answered, number unreadable, payment details including rail used and settlement status, and a receipt URL for the transaction.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input",
  "output"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method"
   ],
   "properties": {
    "body": {
     "type": "object"
    },
    "type": {
     "const": "http"
    },
    "method": {
     "const": "POST"
    },
    "bodyType": {
     "const": "application/json"
    }
   },
   "additionalProperties": true
  },
  "output": {
   "type": "object",
   "required": [
    "type",
    "example"
   ],
   "properties": {
    "type": {
     "const": "json"
    },
    "example": {
     "type": "object"
    }
   },
   "additionalProperties": true
  }
 },
 "additionalProperties": false
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "items": 3,
  "results": [
   {
    "tool": "verify_citation",
    "input": "10.1038/nature12373",
    "verdict": "verified"
   }
  ],
  "answered": 3,
  "paid_with": {
   "rail": "x402_pay_per_call",
   "settlement": {
    "success": true
   },
   "list_price_usd": 0.12
  },
  "by_verdict": {
   "verified": 2,
   "retracted": 1
  },
  "unreadable": 0,
  "receipt_url": "https://factstamp.agentrails.workers.dev/r/c41e77b2aa90d613"
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/factstamp-bulk-verification-a9551a3e/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from factstamp.agentrails.workers.dev](https://www.zero.xyz/host/factstamp.agentrails.workers.dev/llms.txt)