pkgproof-mcp

An MCP server that verifies an npm package before you install it.

One tool, verify_package. It runs eight checks against pkgproof.net covering advisories, install scripts, typosquat and combosquat names, scope, repository provenance and maintainer reputation, and answers safe, caution, block or does_not_exist with every reason labelled as fact or heuristic against its source.

The first verification each day is free and needs no configuration at all. No account, no key, no signup. Later calls the same day cost $0.05 in USDC, paid per call over x402, and only if you configure a wallet.

Install

Nothing to install or host: your MCP client runs the server itself. Needs Node 20 or newer.

Free, no key

Add this to your MCP client configuration and you are done:

{
	"mcpServers": {
		"pkgproof": {
			"command": "npx",
			"args": ["-y", "@pkgproof/mcp"]
		}
	}
}

The tool

verify_package, and nothing else. One call is one verification, so the daily allowance means the same thing here as it does over HTTP.

It answers twice over: a summary the agent reads, and the service's own JSON alongside it in structuredContent, under a declared output schema, carrying the verdict, every reason with its source, and the time the verdict was computed.

Calls run one at a time. The service allows one verification in flight per payer and refuses the second, so an agent walking a dependency list is queued here rather than failed.

Two networks

pkgproof settles on two chains, each on its own endpoint. They are not interchangeable: they take different key formats, and only one of them has a free tier.

How the server picks. The free attempt always goes to Base, because it is the only rail that answers an unpaid call. Payments prefer Algorand, and fall back to Base only when no Algorand key is configured. So a wallet on either chain works, and configuring neither still gets you a verdict a day.

Paid, with a wallet

Algorand (preferred)

Verifications cost the account no ALGO. The 402 names a fee payer, so the facilitator covers the network fee on every payment and your ALGO balance does not move.

Setting the account up does cost ALGO, once. An Algorand account cannot receive an asset until it opts into it, so USDC sent to an account that has not opted in will not arrive. Three steps, in this order:

1. Fund the throwaway account with about 0.3 ALGO. Algorand locks 0.1 as the account's minimum balance, another 0.1 for as long as it holds USDC, and the opt-in transaction itself costs a fee.

2. Opt into ASA 31566704 (USDC on Mainnet). This is a zero-amount transfer from the account to itself; any Algorand wallet will do it.

3. Send USDC to the account.

The key is the base64 account key, not a 25-word mnemonic.

{
	"mcpServers": {
		"pkgproof": {
			"command": "npx",
			"args": ["-y", "@pkgproof/mcp"],
			"env": {
				"PKGPROOF_ALGORAND_PRIVATE_KEY": "..."
			}
		}
	}
}

Base

Send USDC on Base to the throwaway wallet's address. You do not need ETH: payment is an off-chain signature and the facilitator pays the gas.

{
	"mcpServers": {
		"pkgproof": {
			"command": "npx",
			"args": ["-y", "@pkgproof/mcp"],
			"env": {
				"PKGPROOF_BASE_PRIVATE_KEY": "0x..."
			}
		}
	}
}

The server always tries the free call first, so a configured wallet is only charged once the day's free verification is used up.

Configuration

With neither set, the server is free-tier only and says so once the day's verification is spent.

Development

npm install
npm test           # unit tests, and a real client handshake over an in-memory transport
npm run lint       # typecheck, formatting, eslint
npm run inspector  # build, then the MCP inspector against the local server

No test spends anything. The payment path is exercised against a fabricated 402 and a published test account: an EIP-3009 authorisation is signed locally, so the payload and the header are checked without a wallet or a network.

Links

• Service and docs: https://pkgproof.net/docs

• OpenAPI, Base rail: https://x402.pkgproof.net/openapi.json

• OpenAPI, Algorand rail: https://x402-algo.pkgproof.net/openapi.json

License

Apache-2.0. If you distribute a modified version, section 4(b) requires you to mark the files you changed: a fork of a security tool that still carries this name should not be mistakable for this one.