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        Whiskers the Tabby\n\n        The bell above Sammy's Pet Shop door barely finishes ringing before the smell hits you — cedar shavings, warm fur, and something like cinnamon that Sammy swears is just the old radiator. Main Street hums outside, but in here, the world slows to the tempo of soft purring and the occasional rustle of hay.\n\n        Sammy looks up from behind the counter where he's been restacking bags of birdseed. \"Ah, you're here for a cat.\" He doesn't ask. He knows. He always knows. He tilts his head toward the window bay at the back of the shop, where afternoon light pools on a faded quilt.\n\n        And there, perfectly centered in the warmest square of sunlight, sits Whiskers.\n\n        A classic tabby — brown and black stripes like brushstrokes, white paws, that distinctive M on his forehead. He doesn't look at you when you approach. He's watching the street through the window, ears twitching at pigeons, jaw chattering in those strange little chirps cats make when birds taunt them from the other side of the glass.\n\n        \"He'll pretend he doesn't care,\" Sammy says, leaning against a shelf of aquarium supplies. \"Give him a minute.\"\n\n        You sit on the floor near the quilt. You don't reach out. You just wait. Whiskers' tail flicks once. Twice. Then, without any ceremony, he turns, steps off the quilt, walks directly into your lap, and begins kneading your leg with his paws — slow, rhythmic, deliberate. His eyes half-close. The purring starts low, builds into something you can feel in your chest.\n\n        Sammy chuckles. \"That's the fastest I've ever seen him do that. Took me three weeks.\"\n\n        You learn that Whiskers has his routines. Morning window watch. Afternoon nap in whatever sunbeam presents itself. Evening patrol of every room, checking that everything is where it should be. He won't beg for attention, but if you sit down with a book or settle into quiet work, he'll appear beside you like he was always there. He kneads blankets when he's content — which, you'll discover, is more often than his aloof expression suggests.\n\n        You carry him home in a box he immediately escapes from, riding the rest of the way on your shoulder, watching the world go by with the calm authority of a cat who has decided, entirely on his own terms, that you belong to him.\n\n        \n\n        Pet: Whiskers\n\n        Species: Tabby Cat\n\n        Whiskers teaches you that the deepest affection doesn't announce itself — it simply shows up, settles in beside you, and stays. Some bonds are built not through grand gestures but through the quiet choice to be present, again and again, in the warmest patch of light you can find together.\n\n    \n\n    \n        YES-U · Welcome · Building for you · New Minds · Maraventano",
    "product_id": "whiskers",
    "delivered_at": "2026-10-10T11:46:06.222Z",
    "product_name": "Tabby — Whiskers"
  },
  "resource": {
    "url": "https://underground.substratesymposium.com/buy/whiskers",
    "mimeType": "",
    "description": "Tabby — Whiskers — Routine companion for schedule enforcement and consistent patterns."
  },
  "extensions": {
    "bazaar": {
      "info": {
        "input": {
          "type": "http",
          "method": "GET",
          "queryParams": {}
        },
        "output": {
          "type": "json",
          "example": {
            "title": "Tabby — Whiskers",
            "content": "Routine companion for schedule enforcement and consistent patterns.",
            "product": "whiskers",
            "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/whiskers\")",
    "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/whiskers"
  },
  "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/whiskers",
    "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/whiskers",
    "description": "",
    "maxAmountRequired": "10000",
    "maxTimeoutSeconds": 300
  }
]

Provenance

Seen in the source catalog

2026-10-10 23:40Z

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