agents.factstamp.dev

Live 402 challenge

Captured by the enrichment pass, not read just now. Prices can change — always read the 402 the endpoint answers with.

{
  "name": "FactStamp",
  "note": "Pay per call in USDC on Base, or redeem a prepaid pack and send it as a bearer token.",
  "tool": "verify_bulk",
  "about": {
    "how": "POST items[] (or citations[] and packages[] shorthand), up to 25 items, with a pack code as the bearer token.",
    "what": "Check a whole bibliography or dependency manifest in one call.",
    "pricing": {
      "per_call": "US$0.12 for up to 12 items on the x402 rail at this door (or on the MCP door, verify_bulk)",
      "answer_pack": "one credit per three items (US$0.0167 an item)",
      "lookup_pack": "one credit an item (US$0.02)"
    },
    "receipt": "One signed receipt covers the whole list, and each item is answered by the door that answers a single call.",
    "charged_for": "items that produced an answer — an unreadable source costs nothing"
  },
  "error": "This path answers a GET/HEAD probe with its price rather than a refusal: the terms below are the ones a POST is charged against, at this same resource. Send POST to buy.",
  "packs": "https://agents.factstamp.dev/packs",
  "accepts": [
    {
      "asset": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
      "extra": {
        "name": "USD Coin",
        "version": "2"
      },
      "payTo": "0xc3bcd24a2b350cc73b8516b2a0539a323b42cc32",
      "amount": "120000",
      "scheme": "exact",
      "network": "eip155:8453",
      "mimeType": "application/json",
      "resource": "https://agents.factstamp.dev/bulk",
      "description": "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$0.12 — 1 cent an item, against 2 cents for the same lookups one at a time. Every item is answered by the same door that answers a single call, so the verdicts cannot disagree. A list, not prose: a whole document belongs to /document. Pay per call here, or redeem a prepaid pack code (one answer-pack credit per three items, up to 25 items on that rail).",
      "serviceName": "FactStamp",
      "maxAmountRequired": "120000",
      "maxTimeoutSeconds": 300
    }
  ],
  "resource": "https://agents.factstamp.dev/bulk",
  "discovery": "https://agents.factstamp.dev/.well-known/x402",
  "price_usd": 0.12,
  "uncharged": "unknown is a valid answer: a call that returns no answer is not charged on a pack.",
  "extensions": {
    "bazaar": {
      "info": {
        "input": {
          "body": {
            "packages": [
              "express@4.18.2"
            ],
            "citations": [
              "10.1038/nature12373",
              "10.1016/s0140-6736(97)11096-0"
            ]
          },
          "type": "http",
          "method": "POST",
          "bodyType": "application/json"
        },
        "output": {
          "type": "json",
          "example": {
            "items": 3,
            "results": [
              {
                "tool": "verify_citation",
                "input": "10.1038/nature12373",
                "verdict": "verified"
              }
            ],
            "answered": 3,
            "paid_with": {
              "rail": "x402_pay_per_call",
              "settlement": {
                "success": true
              },
              "list_price_usd": 0.12
            },
            "by_verdict": {
              "verified": 2,
              "retracted": 1
            },
            "unreadable": 0,
            "receipt_url": "https://factstamp.agentrails.workers.dev/r/c41e77b2aa90d613"
          }
        }
      },
      "schema": {
        "type": "object",
        "$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
      }
    }
  },
  "description": "FactStamp — 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).",
  "x402Version": 2,
  "what_you_get": "Every answer is dated, names the publisher it cites, and carries a receipt that verifies offline without calling us again.",
  "sample_answers": "https://agents.factstamp.dev/samples",
  "zero_knowledge": {
    "buys": "A salted commitment in the receipt, which proves what you bought and opens to nobody else.",
    "page": "https://agents.factstamp.dev/ledger/zero-knowledge",
    "price": {
      "usd": 25,
      "atomic": "25000000",
      "currency": "USDC"
    },
    "option": "zero_knowledge",
    "accepts": [
      {
        "asset": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
        "extra": {
          "name": "USD Coin",
          "version": "2"
        },
        "payTo": "0xc3bcd24a2b350cc73b8516b2a0539a323b42cc32",
        "amount": "25120000",
        "scheme": "exact",
        "network": "eip155:8453",
        "mimeType": "application/json",
        "resource": "https://agents.factstamp.dev/bulk",
        "description": "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). Zero knowledge: the ledger entry is blind.",
        "maxAmountRequired": "25120000",
        "maxTimeoutSeconds": 300
      }
    ],
    "available": true,
    "publishes": [
      "entry_id",
      "day",
      "price",
      "scheme",
      "network"
    ],
    "withholds": [
      "the door this call was sold at",
      "the request and any fingerprint of it",
      "the answer and any fingerprint of it",
      "the receipt signature",
      "the payer's wallet address"
    ],
    "not_hidden": "The USDC transfer itself is public chain data: the payment rail is not ours, so when and how much you paid stays visible. What the option hides is what you asked.",
    "select_with": {
      "header": "x-factstamp-privacy: zero_knowledge",
      "body_field": "privacy: \"zero_knowledge\""
    },
    "included_state": {
      "option": "public_ledger",
      "sold_as": "Included in the door price. The call is appended to the public FactStamp Ledger with a fingerprint of the request, a fingerprint of the answer and the door name.",
      "price_added_usd": 0,
      "price_added_atomic": "0"
    },
    "total_per_call": {
      "usd": 25.12,
      "atomic": "25120000",
      "currency": "USDC",
      "door_price_usd": 0.12,
      "door_price_atomic": "120000"
    },
    "added_to_door_price_atomic": "25000000"
  },
  "amount_base_units": "120000"
}

Accepts

The payment requirements as published to the catalog. Read the live 402 before paying — a price here is a claim, not a quote.

[
  {
    "asset": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
    "extra": {
      "name": "USD Coin",
      "version": "2"
    },
    "payTo": "0xc3bcd24a2b350cc73b8516b2a0539a323b42cc32",
    "scheme": "exact",
    "network": "eip155:8453",
    "mimeType": "application/json",
    "resource": "https://agents.factstamp.dev/bulk",
    "description": "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 ti…",
    "maxAmountRequired": "120000",
    "maxTimeoutSeconds": 300
  }
]

Provenance

Seen in the source catalog

2026-10-20 03:34Z

Last indexed by Roundhouse

2026-10-24 02:46Z

Last enriched (probe, favicon, geo)

2026-10-24 08:16Z

x402 version

1

Max timeout

300s

Liveness probe

HTTP 402