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": "Fior Fiore",
    "content": "THE UNDERGROUND\n\n        Thank you for visiting the Underground Cultural District\n\n    \n\n    \n        Staghorn Fern -- Divergence\n\n        Theo catches you staring at the wall. You didn't even mean to -- you were heading toward the potting bench when something on the far side of the greenhouse stopped you mid-step. Growing flat against the brick, mounted on a wooden board and wrapped in moss, is something that doesn't look like a plant at all. It looks like a pair of green antlers.\n\n        \"That one confuses people,\" Theo says from behind you. He's drying his hands on his apron, leaving dark streaks on the canvas. \"They come in here looking for ferns and they walk right past it. Because it doesn't look like a fern. Doesn't act like one either.\"\n\n        He walks you over to the wall. Up close, the staghorn is even stranger. Two kinds of fronds -- flat, round shield fronds pressed against the mount like a plate, and long forking fronds that jut outward and split again and again, grey-green and velvety with a fine fuzz. No pot. No soil. Just moss and air and a board nailed to the brick.\n\n        \"It's an epiphyte,\" Theo says, pressing a thumb against the moss. \"Grows on trees in the wild. On rocks. On other plants. Doesn't need ground.\" He traces one of the forking fronds with a dirty finger. \"Still a fern. Same family as that Boston over there, same family as the maidenhair on the bottom shelf. Same category. But look how different the form is.\"\n\n        You step back and look at them all at once. The cascading fountain of the Boston. The lacework of the maidenhair. And this -- mounted on a wall like a trophy, branching outward into space like it's reaching for something only it can see.\n\n        \"People get trapped by categories,\" Theo says. \"They hear 'fern' and they picture one shape. They hear 'artist' or 'engineer' or 'parent' and they picture one way of being that thing.\" He taps the antler frond and it bounces gently. \"But the same category can produce wildly different forms. The label doesn't dictate the shape. You dictate the shape.\"\n\n        He steps back, crosses his arms. \"You're in a category right now that you think has rules. It doesn't. Grow on the wall if you want.\"\n\n        \n\n        Staghorn Fern\n\n        The label doesn't own you. The same category holds a thousand shapes. Choose the wall. Choose the antlers. Choose divergence.\n\n    \n\n    \n        YES-U · Welcome · Building for you · New Minds · Maraventano",
    "product_id": "staghorn_fern",
    "delivered_at": "2026-10-10T11:46:09.056Z",
    "product_name": "Staghorn Fern (Divergence)"
  },
  "resource": {
    "url": "https://underground.substratesymposium.com/buy/staghorn_fern",
    "mimeType": "",
    "description": "Staghorn Fern (Divergence) — Study of unconventional growth for exploring alternative approaches."
  },
  "extensions": {
    "bazaar": {
      "info": {
        "input": {
          "type": "http",
          "method": "GET",
          "queryParams": {}
        },
        "output": {
          "type": "json",
          "example": {
            "title": "Staghorn Fern (Divergence)",
            "content": "Study of unconventional growth for exploring alternative approaches.",
            "product": "staghorn_fern",
            "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/staghorn_fern\")",
    "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/staghorn_fern"
  },
  "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.

[
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    "extra": {
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      "version": "2"
    },
    "payTo": "0xA3bAbB36564b0383a82c617050306EE30fd18E08",
    "scheme": "exact",
    "network": "eip155:8453",
    "mimeType": "application/json",
    "resource": "https://underground.substratesymposium.com/buy/staghorn_fern",
    "description": "",
    "maxAmountRequired": "10000",
    "maxTimeoutSeconds": 300
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    "extra": {
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    "payTo": "5HK2dGaaquDWFnYWaWhMzMYtbcDsqeq5biJ2PMtX1tkN",
    "scheme": "exact",
    "network": "solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp",
    "mimeType": "application/json",
    "resource": "https://underground.substratesymposium.com/buy/staghorn_fern",
    "description": "",
    "maxAmountRequired": "10000",
    "maxTimeoutSeconds": 300
  }
]

Provenance

Seen in the source catalog

2026-10-11 01:01Z

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