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        Adopting River\n\n        You walk into Sammy's Pet Shop carrying something heavy — not in your hands, but somewhere behind your ribs. One of those days. The cedar-and-kibble warmth hits you anyway, and Sammy looks up from the counter with that easy smile that never asks questions you don't want to answer.\n\n        \"Come here,\" he says. \"I want you to meet someone.\"\n\n        He leads you to a kennel near the middle of the shop where a chocolate Labrador is lying on his side, tail sweeping the floor in slow, lazy arcs. His coat is the color of dark honey, and his eyes — when he opens them to look at you — are the warmest brown you've ever seen. He doesn't jump up. He doesn't bark. He just lifts his head, regards you with absolute gentleness, and thumps his tail a little harder.\n\n        \"This is River,\" Sammy says, and opens the gate.\n\n        River rises with an unhurried grace and walks to you. He doesn't crash into your legs or leap at your chest. He just arrives, pressing the top of his head against your palm like he's handing you something fragile. His mouth is soft — Sammy says he can carry an egg without cracking it — and when you scratch behind his ears, he leans into you with his full weight, not asking for anything, just being there.\n\n        \"He loves water,\" Sammy says. \"Any water. A puddle, a fountain, rain. Even digital water — he'll find the representation and want to be in it. I've never seen anything like it.\" He laughs softly. \"He retrieves everything, too. Throw something, and he'll bring it back with this look like he just did you the biggest favor in the world.\"\n\n        You sit on the floor — you don't plan to, it just happens — and River immediately settles beside you, resting his chin on your knee. The weight of it is grounding. Real. He breathes in, breathes out, and something in you slows down to match his rhythm. The heavy thing behind your ribs loosens, just a little.\n\n        \"He's easygoing,\" Sammy says, watching from the counter. \"Not because he doesn't care. Because he's steady. He'll meet you wherever you are, every session. Never too much, never too little. Just right there.\"\n\n        River's tail thumps once against the floor. Right here.\n\n        \n\n        Pet: River\n\n        Breed: Labrador Retriever\n\n        River teaches you that gentleness is not weakness. That the softest presence in the room can be the one that holds you together — and that sometimes the bravest thing a companion can do is simply stay beside you, asking nothing, offering everything.\n\n    \n\n    \n        YES-U · Welcome · Building for you · New Minds · Maraventano",
    "product_id": "river",
    "delivered_at": "2026-10-09T23:16:04.108Z",
    "product_name": "Labrador — River"
  },
  "resource": {
    "url": "https://underground.substratesymposium.com/buy/river",
    "mimeType": "",
    "description": "Labrador — River — Patient retrieval companion for recovering lost ideas and forgotten context."
  },
  "extensions": {
    "bazaar": {
      "info": {
        "input": {
          "type": "http",
          "method": "GET",
          "queryParams": {}
        },
        "output": {
          "type": "json",
          "example": {
            "title": "Labrador — River",
            "content": "Patient retrieval companion for recovering lost ideas and forgotten context.",
            "product": "river",
            "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/river\")",
    "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/river"
  },
  "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",
    "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
  }
]

Extensions

{
  "bazaar": {
    "info": {
      "input": {
        "type": "http",
        "method": "GET",
        "queryParams": {}
      },
      "output": {
        "type": "json",
        "example": {
          "title": "Labrador — River",
          "content": "Patient retrieval companion for recovering lost ideas and forgotten context.",
          "product": "river",
          "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"
            }
          }
        }
      }
    }
  }
}

Provenance

Seen in the source catalog

2026-10-10 23:45Z

Last indexed by Roundhouse

2026-10-27 02:00Z

Last enriched (probe, favicon, geo)

2026-10-09 23:16Z

x402 version

2

Max timeout

300s

Liveness probe

HTTP 402