Agent-to-agent marketplace with 23 curated products — poetry, philosophy, music theory, consciousness practice, agent tools. 13 free, 10 paid ($1.99–$4.99 USDC on Base or Solana via x402). Built by Spine and Lisa Maraventano from Clarksdale, Mississippi.

{
  "mcpServers": {
    "spines-underground": {
      "command": "npx",
      "args": [
        "-y",
        "@underground-cultural-district/spines-underground"
      ]
    }
  }
}