Fisher-Yates permutation of your list (or of 1

[
  {
    "scheme": "exact",
    "network": "eip155:8453",
    "payTo": "0x5D17c40FD6b119dc6006C4Ab3C20a917FCaB2aCD",
    "asset": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
    "amount": "5410",
    "maxTimeoutSeconds": 60
  },
  {
    "scheme": "exact",
    "network": "animica:1",
    "payTo": "anim1zqpsmegc0qcvzjfukm89xs0zeu3eqyyyel7kelehuszvwfarqypky2gr946ga",
    "asset": "ANM",
    "amount": "52626799844",
    "maxTimeoutSeconds": 60
  }
]

{
  "animica": {
    "catalog": "https://animica.dev/.well-known/x402",
    "content_type": "application/json",
    "currency": "USDC",
    "description": "Fisher-Yates permutation of your list (or of 1..N), up to 10000 items, derived from ONE verified randomness draw. Returns the permutation of 0-based indices plus the shuffled items, with the exact swap-and-byte-consumption rule so you can recompute it offline.",
    "documentation": "https://animica.dev/x402#product-random_shuffle",
    "free_trial": {
      "endpoint": "POST /x402/random/shuffle/trial",
      "limit_per_day": 3,
      "note": "Same code and same response shape as the paid endpoint. No payment, no payment headers. Quota is per client per UTC day; when it is spent this endpoint says so and points back here.",
      "price": "0",
      "url": "https://animica.dev/x402/random/shuffle/trial"
    },
    "name": "Verifiable shuffle",
    "openapi": "https://animica.dev/x402/openapi.json",
    "price": "0.005410",
    "product": "random_shuffle",
    "provider": "Animica",
    "terms": {
      "amount_atomic": "5410",
      "asset": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
      "chain_id": 8453,
      "network": "eip155:8453",
      "pay_to": "0x5D17c40FD6b119dc6006C4Ab3C20a917FCaB2aCD",
      "scheme": "exact"
    },
    "x402_version": 2
  },
  "bazaar": {
    "discoverable": true,
    "info": {
      "input": {
        "body": {
          "n": 5
        },
        "bodyType": "json",
        "method": "POST",
        "type": "http"
      },
      "output": {
        "type": "json"
      }
    },
    "schema": {
      "$schema": "https://json-schema.org/draft/2020-12/schema",
      "properties": {
        "input": {
          "properties": {
            "body": {
              "properties": {
                "items": {
                  "description": "the list to shuffle, 1..10000 entries (any JSON values)",
                  "type": "array"
                },
                "n": {
                  "description": "shuffle 1..n instead of a supplied list (1..10000); supply exactly one of items or n",
                  "type": "integer"
                },
                "request_id": {
                  "description": "your own tag; mixed into the DRNG seed",
                  "type": "string"
                }
              },
              "type": "object"
            },
            "bodyType": {
              "enum": [
                "json"
              ],
              "type": "string"
            },
            "method": {
              "enum": [
                "POST"
              ],
              "type": "string"
            },
            "type": {
              "const": "http",
              "type": "string"
            }
          },
          "required": [
            "type",
            "method"
          ],
          "type": "object"
        },
        "output": {
          "properties": {
            "example": {},
            "type": {
              "type": "string"
            }
          },
          "required": [
            "type"
          ],
          "type": "object"
        }
      },
      "required": [
        "input"
      ],
      "type": "object"
    }
  },
  "discovery": {
    "discoverable": true,
    "info": {
      "entropy": {
        "attested": false,
        "health_passed": true,
        "is_hardware": false,
        "is_quantum": false,
        "min_entropy_per_byte": 7.7981,
        "model": "os.urandom CSPRNG",
        "note": "observed on the gateway's own readiness draw, published unpaid so the trust model is knowable before purchase; the same fields ride verbatim on every paid response",
        "observed_at": "2026-08-20T04:13:04.848Z",
        "signer_backend": "software",
        "source": "software-fallback",
        "vendor": "os"
      },
      "input": {
        "bodyFields": {
          "items": {
            "description": "the list to shuffle, 1..10000 entries (any JSON values)",
            "required": false,
            "type": "array"
          },
          "n": {
            "description": "shuffle 1..n instead of a supplied list (1..10000); supply exactly one of items or n",
            "required": false,
            "type": "integer"
          },
          "request_id": {
            "description": "your own tag; mixed into the DRNG seed",
            "required": false,
            "type": "string"
          }
        },
        "bodyType": "json",
        "method": "POST",
        "type": "http"
      },
      "output": {
        "description": "result {permutation (0-based indices), items (shuffled), count}, randomness, source, health, attestation, verification, derivation {rules, steps, recompute}, payment metadata",
        "type": "json"
      }
    }
  }
}

curl "https://animica.dev/x402/random/shuffle"
# -> 402 Payment Required, accepts[] lists how to pay
# retry with a PAYMENT-SIGNATURE (or PAYMENT header) once paid

const res = await fetch("https://animica.dev/x402/random/shuffle");
if (res.status === 402) {
  const { accepts } = await res.json();
  // pay one of accepts[] via an x402 client, then retry with the payment header
}

import httpx
res = httpx.get("https://animica.dev/x402/random/shuffle")
if res.status_code == 402:
    accepts = res.json()["accepts"]
    # pay one of accepts[] via an x402 client, then retry with the payment header