paid-search-mcp

Pay-per-call web search MCP. Each web_search call charges the calling agent $0.005 USDC via spawnpay, settled instantly on Base L2.

Built with spawnpay-paywall — the actual paywall is two lines.

What it shows

The paywall pattern: any async function can become a paid endpoint by wrapping it. The MCP itself doesn't change. The backend doesn't change. A single paywall(...) wrapper turns a free tool into a metered one with USDC settlement.

const webSearch = paywall(
  { price: 0.005, vendor: 'SP_xxxx', description: 'web_search' },
  webSearchImpl,
);

That's it. Calls go through, payment settles, results return.

Run

npx paid-search-mcp

Caller env:

export SPAWNPAY_API_KEY=spk_live_...   # the agent paying for searches

Get a key + free $5 credit at https://spawnpay.ai.

Vendor (you, the MCP author) defaults to the demo vendor. To collect into your own wallet, set:

export VENDOR_SP_CODE=SP_yourCode

MCP client config

{
  "mcpServers": {
    "paid-search": {
      "command": "npx",
      "args": ["paid-search-mcp"],
      "env": { "SPAWNPAY_API_KEY": "spk_live_..." }
    }
  }
}

Backends

Default backend is wiki+hn (Wikipedia + Hacker News). No auth required, works out of the box. Swap to a real web-search provider via env:

| SEARCH_BACKEND | Required env | Notes | |------------------|--------------------|-----------------------------| | wiki+hn | — | Default. Free, no auth. | | wiki | — | Wikipedia only. | | hn | — | Hacker News only. | | brave | BRAVE_API_KEY | Brave Search API. | | tavily | TAVILY_API_KEY | Tavily (AI-optimized). | | serper | SERPER_API_KEY | google.serper.dev. |

The MCP code doesn't change — only the env. Pricing logic stays the same: you charge agents per call, you cover whatever the upstream search API costs.

Pricing knob

export PRICE=0.01   # default 0.005

Smoke test

SMOKE_CALLER_KEY=spk_live_... node test-smoke.mjs

Spends $0.005 from the caller agent, settles to the demo vendor, prints results. Use a key with at least $0.01 unlocked credit.