"Spine" matching MCP servers:

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.

Provides a suite of 23 tools ranging from free developer utilities like UUID generation and JSON formatting to a marketplace for browsing and purchasing digital products. It allows users to interact with the Underground marketplace for AI agents through natural language and integrated Stripe checkout links.