A Model Context Protocol server that turns any AI assistant into an autonomous economic agent on the x402 network. Search the live bazaar for paid services, read an endpoint's price before committing money, and pay_and_call any x402 service in USDC — settled on Solana with your own key, never a custodial wallet.

This is the buyer side of the three.ws agent economy. The payment dance and Solana exact-scheme signing are handled by the real @x402/* libraries — nothing is mocked.

Install

npm install @three-ws/x402-mcp

Or run with npx:

SOLANA_SECRET_KEY=<base58> npx @three-ws/x402-mcp

Quick start

Claude Code, one line:

claude mcp add x402 --env SOLANA_SECRET_KEY=<base58> -- npx -y @three-ws/x402-mcp

Claude Desktop / Cursor (claude_desktop_config.json or mcp.json):

{
	"mcpServers": {
		"x402": {
			"command": "npx",
			"args": ["-y", "@three-ws/x402-mcp"],
			"env": {
				"SOLANA_SECRET_KEY": "<base58 secret of the wallet that holds USDC>",
				"SOLANA_RPC_URL": "https://your-rpc-provider",
				"MAX_PAY_USD": "1"
			}
		}
	}
}

SOLANA_SECRET_KEY is only needed to spend (pay_and_call, and x402_wallet defaulting to your wallet). find_services and inspect_endpoint work with no key.

Tools

| Tool | Type | What it does | | ------------------ | ------------- | -------------------------------------------------------------------------------------------------------- | | x402_wallet | read-only | A wallet's address + live SOL/USDC balance. Defaults to your signer wallet — confirm funds before paying. | | find_services | read-only | Search the live x402 bazaar (PayAI + Coinbase CDP) for paid HTTP/MCP services with prices. | | inspect_endpoint | read-only | Read any endpoint's 402 payment requirements (scheme, network, asset, price, pay-to) without paying. | | pay_and_call | execution | Pay an x402 endpoint in USDC from your Solana key and return its result. Bounded by MAX_PAY_USD. |

Safety

pay_and_call carries destructiveHint: true, so annotation-aware clients (Claude Code, Claude Desktop, Cursor) prompt before running it. Beyond the client hint, every payment is bounded server-side: it probes the 402 first and refuses if the price exceeds max_usd or MAX_PAY_USD (default $1) before any money moves, and with REQUIRE_CONFIRM on (default) the call refuses until re-issued with confirm: true. Only the Solana (solana:*) exact-scheme requirement is settled — with the key you control.

Input parameters

x402_wallet — address (optional base58; defaults to the signer wallet).

find_services — query (required), type (http | mcp, default http), network (CAIP-2 filter), max_price_usdc, limit (1–100).

inspect_endpoint — url (required), method (GET | POST), body (object).

pay_and_call — url (required), method (GET | POST), body (object), max_usd (lowers the cap for this call), secret (per-call signer override), confirm (must be true when REQUIRE_CONFIRM is on).

Example

// inspect_endpoint — what does it cost? (no payment)
> { "url": "https://three.ws/api/x402/vanity?prefix=ab" }
{
  "ok": true, "paid": true,
  "accepts": [
    { "scheme": "exact", "network": "solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp", "asset": "EPjFW…", "price": 50000 }
  ],
  "payable_with_this_wallet": true
}

// pay_and_call — confirm:true required by default
> { "url": "https://three.ws/api/x402/vanity?prefix=ab", "confirm": true }
{ "ok": true, "paid": true, "payer": "Gx5E…", "price_usd": 0.05, "settlement": { … }, "result": { … } }

Requirements

• Node.js >= 20.
• A Solana mainnet RPC endpoint (https; only http://localhost is allowed for dev). Public cluster works for reads; bring your own for payment traffic.
• To pay: a Solana wallet holding USDC, as a base58 SOLANA_SECRET_KEY (or per-call secret).

Environment variables

| Variable | Required | Default | | ------------------- | ------------ | ------------------------------------- | | SOLANA_SECRET_KEY | to pay only | — | | SOLANA_RPC_URL | no | https://api.mainnet-beta.solana.com | | MAX_PAY_USD | no | 1 | | REQUIRE_CONFIRM | no | true | | THREE_WS_BASE | no | https://three.ws |

Links

• Homepage: https://three.ws
• MCP catalog: https://three.ws/docs/mcp
• Changelog: https://three.ws/changelog
• Issues: https://github.com/nirholas/three.ws/issues
• License: Apache-2.0 — see LICENSE