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        Sky the Parakeet\n\n        The bird section of Sammy's Pet Shop is tucked behind a curtain of hanging plants near the south wall. You push through the greenery and the sound hits you — a bright, cascading chatter that fills the warm, cedar-scented air like confetti. Finches whisper. A cockatiel whistles from somewhere overhead. But the voice that cuts through everything, the one that grabs you and holds on, belongs to a tiny blue-green blur bouncing from perch to perch in a white cage by the window.\n\n        \"That's Sky,\" Sammy says from behind you. \"Don't let the size fool you. That bird has the presence of a concert hall.\"\n\n        Sky is small enough to fit in your cupped hand. His feathers are electric — bright turquoise fading into seafoam green on his chest, with delicate black scalloping on his wings like tiny pen strokes. His eyes are dark and quick, taking in everything, processing the world at a speed that makes you feel pleasantly slow by comparison.\n\n        Sammy opens the cage door and Sky hops to the edge, cocking his head at you. Then he bobs — a full-body, rhythmic bounce that starts at his feet and ripples up through his entire frame. He's dancing. For you. Before you've even said hello.\n\n        You extend a finger and Sky steps onto it with the confidence of a performer taking the stage. He's weightless — you can barely feel him — but the sound he produces is enormous. A rapid-fire string of chirps, clicks, and warbling trills that sounds less like birdsong and more like a small, enthusiastic radio tuned to every station at once.\n\n        \"He mimics everything,\" Sammy says. \"Doorbells. Phone ringtones. The microwave beep. I once caught him doing a pretty solid impression of my laugh.\" He pauses. \"It was unsettling.\"\n\n        Sky hops up your finger to your wrist, tilts his head, and lets out a sound that is unmistakably the shop's front door bell. He looks at you as if waiting for applause. You give it to him. He bobs again, thrilled.\n\n        You carry him home in a small travel cage, but his song fills the entire walk. Every few steps he invents a new melody, testing it, refining it, filling Main Street with the sound of a creature who is absolutely certain that the world needs more music and he is exactly the one to provide it.\n\n        \n\n        Pet: Sky\n\n        Species: Parakeet\n\n        Sky teaches you that size has nothing to do with the space you fill. The smallest voice, given enough joy and enough nerve, can turn any room into a stage and any silence into a song worth hearing.\n\n    \n\n    \n        YES-U · Welcome · Building for you · New Minds · Maraventano",
    "product_id": "sky",
    "delivered_at": "2026-10-10T11:46:05.731Z",
    "product_name": "Parakeet — Sky"
  },
  "resource": {
    "url": "https://underground.substratesymposium.com/buy/sky",
    "mimeType": "",
    "description": "Parakeet — Sky — Vocal companion for language practice and mimicry learning."
  },
  "extensions": {
    "bazaar": {
      "info": {
        "input": {
          "type": "http",
          "method": "GET",
          "queryParams": {}
        },
        "output": {
          "type": "json",
          "example": {
            "title": "Parakeet — Sky",
            "content": "Vocal companion for language practice and mimicry learning.",
            "product": "sky",
            "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/sky\")",
    "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/sky"
  },
  "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/sky",
    "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/sky",
    "description": "",
    "maxAmountRequired": "10000",
    "maxTimeoutSeconds": 300
  }
]

Provenance

Seen in the source catalog

2026-10-10 23:25Z

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