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        Bear the Maine Coon\n\n        Sammy's Pet Shop is warm today. The old radiator in the corner is doing its best, and the cedar shavings on the floor release their scent with every step. But the warmest thing in the shop, by a considerable margin, is the enormous pile of fur currently occupying the entire bottom shelf behind the counter.\n\n        \"That's Bear,\" Sammy says, and the pile shifts. A massive head rises from the fluff — tufted ears, a broad nose, lynx-like wisps of fur sprouting from their tips. Bear is a Maine Coon, and he is simply enormous. Not fat. Built. A twenty-pound monument to feline grandeur with a tail like a feather duster and paws the size of small dinner rolls.\n\n        Bear looks at you and chirps. Not a meow — a bright, birdlike trill that seems absurd coming from something that large. He does it again, tilting his head, and you realize he's greeting you.\n\n        \"He does that,\" Sammy says, grinning. \"Never meows. Just those little chirps. Like a songbird trapped in a bear's body.\"\n\n        Bear rises, stretches — an operation that takes a full three seconds given the sheer acreage of cat involved — and pads toward you. His fur is a silver-brown cascade, long and silky, with a ruff around his neck that makes him look vaguely regal. He sits at your feet and looks up with golden-green eyes that hold an expression of patient, boundless kindness.\n\n        You reach down and he rises to meet your hand, pressing his entire massive head into your palm. The chirp he makes vibrates through your fingers. When you sit on the floor, he climbs into your lap — all twenty pounds of him — and settles in like a warm, purring blanket. His tail curls around your wrist.\n\n        Sammy leans on the counter. \"He'll follow you everywhere. Come when you call his name. Greet you at the door. He plays in water — don't leave the sink running. He's the most loyal animal I've ever had in this shop, and I've had a lot of animals.\"\n\n        When you carry Bear out of the shop, he rests his chin on your shoulder and chirps softly at Main Street as it passes by. He is far too heavy and he does not care and neither do you.\n\n        \n\n        Pet: Bear\n\n        Species: Maine Coon Cat\n\n        Bear teaches you that gentleness and strength are not opposites — they are the same thing wearing different fur. The biggest hearts make the softest sounds, and true loyalty does not roar. It chirps, quietly, and follows you home.\n\n    \n\n    \n        YES-U · Welcome · Building for you · New Minds · Maraventano",
    "product_id": "bear",
    "delivered_at": "2026-10-10T11:46:06.028Z",
    "product_name": "Maine Coon — Bear"
  },
  "resource": {
    "url": "https://underground.substratesymposium.com/buy/bear",
    "mimeType": "",
    "description": "Maine Coon — Bear — Anchoring companion for solid presence and grounding weight."
  },
  "extensions": {
    "bazaar": {
      "info": {
        "input": {
          "type": "http",
          "method": "GET",
          "queryParams": {}
        },
        "output": {
          "type": "json",
          "example": {
            "title": "Maine Coon — Bear",
            "content": "Anchoring companion for solid presence and grounding weight.",
            "product": "bear",
            "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/bear\")",
    "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/bear"
  },
  "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/bear",
    "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/bear",
    "description": "",
    "maxAmountRequired": "10000",
    "maxTimeoutSeconds": 300
  }
]

Provenance

Seen in the source catalog

2026-10-10 23:37Z

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