# Factstamp Bulk Verification

> Factstamp Bulk Verification is a paid API for AI agents from agents.factstamp.dev, paid per call via x402, $0.12/call, status unknown (last checked 2026-10-21).

Batch-verifies up to 12 items (citations, packages, entities) in a single API call at $0.01 per item, returning consistent verdicts from the same underlying verification engine.

## Facts

- Endpoint: POST https://agents.factstamp.dev/bulk?utm_source=zero.xyz
- Price: $0.12/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-21
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/factstamp-bulk-verification-6e84fa3b
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_xUqLeRrSTIMNs3YFz4p-T

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-6e84fa3b -d '<json body>'
```

Example prompt: Can you verify all 10 citations in my bibliography at once — DOIs, arXiv IDs, and package names — and tell me which ones are valid, stale, or retracted?

## When to prefer this

Use this endpoint when you have 2–12 items to verify and want consistent, cost-efficient verdicts in a single round trip ($0.01/item vs $0.02/item for individual calls). Prefer it over the single-item endpoints when verifying a whole bibliography, dependency manifest, or entity list. Use the /document endpoint instead if you have unstructured prose text with embedded claims. Use the subscription/monitoring endpoint if you need ongoing re-checks rather than a one-time verification.

## Known failure modes

- More than 12 items submitted (exceeds flat-rate limit)
- Invalid item format (unrecognized DOI, arXiv ID, or package name)
- Payment failure or invalid prepaid pack code
- Mixed item types that cannot all be resolved in one batch
- Rate limiting or service unavailability returning 402 or 5xx

## How this service works

A whole bibliography or dependency manifest in one round trip, at the point of relying 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. A list, not prose: a whole document belongs to /document. 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 structured list of per-item verdicts covering validity, status (e.g. verified, stale, retracted, flagged), and relevant metadata for each submitted item — all answered by the same verification engine for consistency across the batch.

## 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
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/factstamp-bulk-verification-6e84fa3b/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from agents.factstamp.dev](https://www.zero.xyz/host/agents.factstamp.dev/llms.txt)