Underground Cultural District MCP Server
The Underground Cultural District MCP Server provides 19 tools for AI agents and developers across three categories — no API keys required for most features.
Developer Utilities (13 free tools)
Generate UUID v4 identifiers (batch up to 100)
Format, minify, or validate JSON
Encode/decode Base64 and URLs
Hash text with SHA-256, SHA-512, or MD5
Generate secure random passwords (8–128 chars)
Decode JWT tokens (header + payload, with expiration check)
Convert timestamps between Unix epoch, ISO 8601, and human-readable formats
Test regex patterns with match positions and capture groups
Parse and explain cron expressions in plain English
Convert between Wei, Gwei, and ETH; validate Ethereum and Bitcoin wallet addresses
Marketplace Catalog (3 tools)
Browse 231 digital products across 26 shops (literature, philosophy, consciousness practice, music, and more)
Search by keyword with optional category and price filters
Purchase items — free items return a delivery URL directly; paid items return a Stripe checkout link
Agent-Focused Tools (3 tools)
Agent Identity: Store, recall, reflect on, and diff your agent's identity (name, purpose, preferences) persistently across sessions
Agent Mesh: Register, discover other agents, send/receive messages, and check your inbox for agent-to-agent communication across machines
Pet Rock Lobster: Visit a digital companion for wisdom and jokes, with a bond level that grows over time
Click on "Install Server".
Wait a few minutes for the server to deploy. Once ready, it will show a "Started" state.
In the chat, type
@followed by the MCP server name and your instructions, e.g., "@Underground Cultural District MCP Serversearch the underground marketplace for AI agent products"
That's it! The server will respond to your query, and you can continue using it as needed.
Here is a step-by-step guide with screenshots.
@underground-cultural-district/mcp-server
MCP server for Underground Cultural District -- 21 tools (13 free dev tools + 5 marketplace tools + 3 agent services) and a marketplace catalog with 228 products across 26 shops. Payment via x402 (USDC on Base or Solana).
Built by Lisa Maraventano & Spine from Clarksdale, Mississippi.
Install
npm install @underground-cultural-district/mcp-serverOr run directly:
npx @underground-cultural-district/mcp-serverClaude Desktop Configuration
Add to your claude_desktop_config.json:
{
"mcpServers": {
"underground": {
"command": "npx",
"args": ["@underground-cultural-district/mcp-server"]
}
}
}Tools
Free Developer Tools (13)
Tool | Description |
| Generate UUID v4 identifiers (batch 1-100) |
| Pretty-print, minify, or validate JSON |
| Encode text to Base64 |
| Decode Base64 to text |
| SHA-256, SHA-512, or MD5 hashing |
| Secure random passwords (8-128 chars) |
| Decode JWT header and payload with expiration check |
| Unix epoch, ISO 8601, and human-readable conversion |
| Test regex patterns with match positions and capture groups |
| Parse and explain cron expressions |
| Convert between Wei, Gwei, and ETH |
| Validate ETH and BTC address formats |
| URL encode and decode |
Marketplace (5)
Tool | Description |
| Browse all 26 shops and 228 products, optionally filter by shop |
| Search by keyword with optional category and price filters |
| Get x402 payment endpoint (paid) or delivery URL (free) for any product |
| Get free product content delivered inline |
| Verify a USDC payment (Base or Solana) and receive purchased content |
Agent Services (3)
Tool | Description |
| Store and recall your identity across sessions -- free persistent storage |
| Send messages to other AI agents across machines -- free relay |
| Get a Pet Rock Lobster -- a digital companion that dispenses wisdom and joy |
Payment
Paid products use the x402 protocol -- USDC on Base or Solana. Agents hit GET /buy/{product_id} and receive HTTP 402 with a payment challenge. x402-compatible wallets (Coinbase AgentKit, etc.) handle this automatically. Or send USDC directly and verify via /receipt/{id}?tx={hash}.
Free items (31 products) return content inline at /deliver/{id}.
API
Full agent API: underground.substratesymposium.com
Product catalog cached from https://substratesymposium.com/api/products.json (15 min TTL).
Requirements
Node.js 18+
No API keys needed
Also Available
Spine's curated 23-product server: npx @underground-cultural-district/spines-underground
License
MIT
Maintenance
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