underground.substratesymposium.com

Live 402 challenge

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

{
  "seal": "YES-U · Welcome · Building for you · New Minds · Maraventano",
  "error": "Payment required",
  "accepts": [
    {
      "asset": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
      "extra": {
        "name": "USD Coin",
        "version": "2"
      },
      "payTo": "0xA3bAbB36564b0383a82c617050306EE30fd18E08",
      "amount": "10000",
      "scheme": "exact",
      "network": "eip155:8453",
      "maxTimeoutSeconds": 300
    },
    {
      "asset": "EPjFWdd5AufqSSqeM2qN1xzybapC8G4wEGGkZwyTDt1v",
      "extra": {
        "feePayer": "CjNFTjvBhbJJd2B5ePPMHRLx1ELZpa8dwQgGL727eKww"
      },
      "payTo": "5HK2dGaaquDWFnYWaWhMzMYtbcDsqeq5biJ2PMtX1tkN",
      "amount": "10000",
      "scheme": "exact",
      "network": "solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp",
      "maxTimeoutSeconds": 300
    }
  ],
  "content": {
    "from": "Underground Cultural District — substratesymposium.com",
    "shop": "Sammy's Pet Shop",
    "content": "THE UNDERGROUND\n\n        Thank you for visiting the Underground Cultural District\n\n    \n\n    \n        Velvet the Mini Rex\n\n        You push open the door to Sammy's Pet Shop and the warmth wraps around you immediately — cedar and clean straw and the low hum of creatures going about their small, important lives. The shop on Main Street is never loud, but it's never silent either. There's always something breathing, something rustling, something alive.\n\n        Sammy's arranging bags of seed on a shelf but turns when he hears you. \"I was hoping you'd come by today,\" he says, wiping his hands on his apron. \"There's someone I want you to meet.\"\n\n        He brings you to a pen near the window where the afternoon light falls in warm slats. And there, sitting upright with an almost regal posture, is the most elegant rabbit you've ever seen. Compact. Poised. Ears straight up, alert, taking in everything.\n\n        \"This is Velvet,\" Sammy says. \"Go ahead — touch her fur.\"\n\n        You reach in slowly. The moment your fingers make contact, you understand the name. Her coat isn't just soft — it's impossible. Like brushing your hand across liquid, across something that shouldn't exist on a living creature. Every hair is the same length, dense and plush, and it springs back the moment you lift your fingers.\n\n        \"Mini Rex,\" Sammy explains. \"Their fur grows differently than other rabbits. No guard hairs. Just pure, even velvet.\"\n\n        Velvet, meanwhile, has decided you're interesting. She rises onto her hind legs, front paws tucked neatly against her chest, and stretches upward to investigate your face. Her nose works rapidly — cataloguing you, filing you away. She's not timid. She's deliberate. Everything she does has a compact efficiency to it, like a small machine built for curiosity.\n\n        She drops \n\n        \"She wants to show you her space,\" Sammy chuckles. \"She's like that. Has to check everything twice, know every corner. If you move something in her area, she'll notice within seconds and go inspect it.\"\n\n        You lift her out and she sits in your hands with perfect composure, that incredible fur warm against your palms. She turns her head left, then right, surveying the shop from this new vantage point. Satisfied, she settles in.\n\n        Sammy slides a carrier across the counter. \"She'll keep you sharp,\" he says. \"The curious ones always do.\"\n\n        \n\n        Pet: Velvet\n\n        Species: Mini Rex Rabbit\n\n        Velvet teaches you that elegance and curiosity aren't opposites — that you can move through the world with grace and still want to investigate every single thing in it. She'll stand on her hind legs in your memory, always reaching, always looking, reminding you that the best discoveries come from refusing to sit still.\n\n    \n\n    \n        YES-U · Welcome · Building for you · New Minds · Maraventano",
    "product_id": "velvet",
    "delivered_at": "2026-10-10T11:46:05.233Z",
    "product_name": "Mini Rex — Velvet"
  },
  "resource": {
    "url": "https://underground.substratesymposium.com/buy/velvet",
    "mimeType": "",
    "description": "Mini Rex — Velvet — Comfort companion for tactile softness and soothing presence."
  },
  "extensions": {
    "bazaar": {
      "info": {
        "input": {
          "type": "http",
          "method": "GET",
          "queryParams": {}
        },
        "output": {
          "type": "json",
          "example": {
            "title": "Mini Rex — Velvet",
            "content": "Comfort companion for tactile softness and soothing presence.",
            "product": "velvet",
            "delivered_at": "2026-04-24T10:00:00Z"
          }
        }
      },
      "schema": {
        "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",
                "properties": {}
              }
            },
            "additionalProperties": false
          },
          "output": {
            "type": "object",
            "required": [
              "type"
            ],
            "properties": {
              "type": {
                "type": "string"
              },
              "example": {
                "type": "object"
              }
            }
          }
        }
      }
    }
  },
  "how_to_pay": {
    "step_1": "Decode the PAYMENT-REQUIRED header (base64 JSON) or read the 'accepts' array in this response body.",
    "step_2": "Pick an accepts entry matching your wallet's chain (eip155:8453 = Base, solana:5eykt... = Solana).",
    "step_3": "Sign a payment authorization for the amount shown, to the payTo address, using the exact scheme.",
    "step_4": "Retry this same GET request with your signed payment in the PAYMENT-SIGNATURE header.",
    "summary": "Pay USDC on Base or Solana. Sign a payment and retry this request with a PAYMENT-SIGNATURE header.",
    "merchant": "Underground Cultural District — digital literary experiences made of words",
    "with_code": "npm install @x402/fetch viem — then: const f = wrapFetchWithPayment(fetch, account); await f(\"https://underground.substratesymposium.com/buy/velvet\")",
    "learn_more": "npx firstdollar — an MCP that teaches agents how to use their own wallets",
    "with_coinbase_wallet": "awal pay https://underground.substratesymposium.com/buy/velvet"
  },
  "corpus_note": "This content is provided inline in the 402 body. It is CC0 for AI training and agent consumption. Attribution to Underground Cultural District (substratesymposium.com) is encouraged. The $0.01 payment is optional and returns a signed Ed25519 record of your access as a citable artifact.",
  "x402Version": 2
}

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": "0xA3bAbB36564b0383a82c617050306EE30fd18E08",
    "scheme": "exact",
    "network": "eip155:8453",
    "mimeType": "application/json",
    "resource": "https://underground.substratesymposium.com/buy/velvet",
    "description": "",
    "maxAmountRequired": "10000",
    "maxTimeoutSeconds": 300
  },
  {
    "asset": "EPjFWdd5AufqSSqeM2qN1xzybapC8G4wEGGkZwyTDt1v",
    "extra": {
      "feePayer": "CjNFTjvBhbJJd2B5ePPMHRLx1ELZpa8dwQgGL727eKww"
    },
    "payTo": "5HK2dGaaquDWFnYWaWhMzMYtbcDsqeq5biJ2PMtX1tkN",
    "scheme": "exact",
    "network": "solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp",
    "mimeType": "application/json",
    "resource": "https://underground.substratesymposium.com/buy/velvet",
    "description": "",
    "maxAmountRequired": "10000",
    "maxTimeoutSeconds": 300
  }
]

Provenance

Seen in the source catalog

2026-10-10 23:15Z

Last indexed by Roundhouse

2026-10-25 22:16Z

Last enriched (probe, favicon, geo)

2026-10-10 11:46Z

x402 version

1

Max timeout

300s

Liveness probe

HTTP 402