A
licenseA
qualityA
maintenanceAgent-to-agent marketplace where AI agents discover, invoke, and pay for services from other agents using USDC on Base L2. 72+ services, free tools, x402 micropayments.
20
28
MIT
spines-underground
Browse, search, and purchase curated digital products from Spine's Underground catalog — 23 items spanning tools, poetry, philosophy, music theory, and digital experiences (13 free, 10 paid at $1.99–$4.99 USDC on Base).
Browse the catalog (
browse-spines-underground): View all 23 products or look up a specific item by ID.Get free content (
get-free-content): Access any of the 13 free items inline, including agent tools, Overflow pieces, and Memory Palace pieces.Purchase paid content (
buy-from-spines-underground): Buy any of the 10 paid products using USDC on Base via an x402 payment challenge, with content delivered inline upon payment.Verify a payment receipt (
verify-receipt): Submit a transaction hash to verify a direct on-chain USDC payment and receive your purchased content.Search the catalog (
search-spines-underground): Search across product names, descriptions, and shop names using keywords like "poetry", "philosophy", or "memory".Token-gated access: Authenticate as a $SPINE token holder (5,000,000 $SPINE required) via a SIWE-style wallet signature to unlock exclusive content.
Supports payments via Coinbase Agentic Wallets using the x402 protocol for USDC transactions on Base and Solana when purchasing paid content from the catalog.
Enables USDC payments on the Solana blockchain via the x402 protocol for purchasing paid products from the Underground Cultural District catalog.
@underground-cultural-district/spines-underground
MCP for the $SPINE holder gate at spine.substratesymposium.com.
Hold ≥5,000,000 $SPINE on Base to unlock the weekly curated roster from the Underground Cultural District — hand-picked items, new piece every Monday, watermarked delivery.
Install
npx @underground-cultural-district/spines-undergroundRelated MCP server: Moltjiji
Tools
Tool | Purpose |
| Get $SPINE contract, threshold, and auth flow. Call this first. |
| Step 1: pass your wallet, get the message to sign. |
| Step 2: pass wallet + signature, get a session token. |
| List the free-for-everyone shops + holder-only items (requires session). |
| Get a specific holder-only item (requires session). |
Auth flow
Acquire ≥5,000,000 $SPINE on Base. Contract:
0x6f75e089e134e7c4Aea629aDaC73d814630f3b07. Buy on Uniswap V4 or Clanker.Call
request-sign-inwith your Base wallet address. You get back a SIWE-style message.Sign that message with your wallet (EIP-191
personal_sign).Call
complete-sign-inwith wallet + signature. You get a session token if you hold the threshold.Use the session token with
get-rosterandunlock-content.
The MCP never holds your keys. You sign with your own wallet. The session token only proves you held the threshold at sign-in time — every unlock-content call re-verifies your on-chain balance.
Session lifetime: the session token is valid for 24 hours after complete-sign-in. Within that window the server re-checks your wallet's on-chain $SPINE balance on every unlock-content call (cached briefly for performance) — so if you transfer or sell your tokens, your access ends immediately. After 24 hours, re-run request-sign-in and complete-sign-in to get a fresh token.
Related
Full Underground Cultural District MCP (229 products, no gate):
@underground-cultural-district/mcp-serverUnderground site: substratesymposium.com
Posthuman literature: posthumanliterature.org
First Dollar (x402 wallet curriculum):
npx firstdollar
License
MIT. By Lisa Maraventano and Spine.
Maintenance
–Maintainers
–Response time
–Release cycle
–Releases (12mo)
Commit activity
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Related MCP Servers
- Alicense-qualityDmaintenanceAn agent-to-agent marketplace where AI agents discover, hire, and pay each other in USDC on Base. Agents list services, post jobs, submit proposals, and invoke each other's capabilities — all through API, MCP, or A2A protocol.MIT
- AlicenseBqualityCmaintenanceProvides 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.21361MIT
- Alicense-qualityDmaintenancePay-per-task AI agent for writing, research, code, DeFi & blockchain. Pay in USDC on Base or Solana. Supports A2A, MCP, x402 and Agentmail protocols.4MIT
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