How do I install Paystage?

Paystage is a local plugin. Install it using npm package: @paystage/auth-watch and add the generated configuration snippet to your AI app's MCP config file. Then restart your AI app.

Is Paystage safe to use?

Yes. Paystage passed MCP Marketplace's automated security scan with a score of 9.7/10 (low risk). Every server on MCP Marketplace is security-scanned before it's listed; see the full security report on this page for the findings and permissions.

What credentials does Paystage need?

Paystage requires the following credentials or environment variables: PAYSTAGE_POLICY_PATH, PAYSTAGE_RPC_URL. You can find setup instructions on the server detail page.

What AI apps work with Paystage?

Paystage uses the Model Context Protocol (MCP) and works with any MCP-compatible AI app, including Claude, ChatGPT / Codex, Gemini, Copilot, Cursor, and more.

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Paystage MCP Server

by Base Buzz

Developer ToolsLow Risk9.7MCP RegistryLocal

Free

Server data from the Official MCP Registry

Read-only MCP tools to list and flag outstanding ERC-20, Permit2, and EIP-3009 auths

About

Read-only MCP tools to list and flag outstanding ERC-20, Permit2, and EIP-3009 auths

Security Report

9.7

Low Risk9.7Low Risk

Valid MCP server (4 strong, 7 medium validity signals). No known CVEs in dependencies. ⚠️ Package registry links to a different repository than scanned source. Imported from the Official MCP Registry. 1 finding(s) downgraded by scanner intelligence.

16 files analyzed · 1 issue found

Security scores are indicators to help you make informed decisions, not guarantees. Always review permissions before connecting any MCP server.

Permissions Required

This plugin requests these system permissions. Most are normal for its category.

env_vars

Check that this permission is expected for this type of plugin.

What You'll Need

Set these up before or after installing:

Path to policy.json spending rulesOptional

Environment variable: PAYSTAGE_POLICY_PATH

Base RPC URL overrideOptional

Environment variable: PAYSTAGE_RPC_URL

How to Install

Add this to your MCP configuration file:

{
  "mcpServers": {
    "xyz-paystage-auth-watch": {
      "env": {
        "PAYSTAGE_RPC_URL": "your-paystage-rpc-url-here",
        "PAYSTAGE_POLICY_PATH": "your-paystage-policy-path-here"
      },
      "args": [
        "-y",
        "@paystage/auth-watch"
      ],
      "command": "npx"
    }
  }
}

Documentation

View on GitHub

From the project's GitHub README.

PayStage

Safety tools for AI agent payments (x402 + MCP).

PayStage sits in front of an agent's wallet and answers one question before money moves: should this payment happen? Tools return pay, review, or do_not_pay.

Quick start

# Option 1: run instantly
npx -y @paystage/mcp

# Option 2: install locally, then use the package bin
npm install @paystage/mcp
npx paystage-mcp

The server waits silently for an agent app to connect. That's normal; press Ctrl+C to exit. To try the tools without an app, run npx @modelcontextprotocol/inspector npx -y @paystage/mcp.

@paystage/mcp 0.3.0 is the umbrella MCP server (5 tools, including evaluate_hip3_trade and evaluate_velocity). It exposes the PayStage tools over stdio and reads a local policy file. See SECURITY.md for exactly what it accesses and why.

Listed on

Configure

The same MCP config works for Claude Desktop (claude_desktop_config.json) and Cursor (.cursor/mcp.json).

Using npx

{
  "mcpServers": {
    "paystage": {
      "command": "npx",
      "args": ["-y", "@paystage/mcp"],
      "env": {
        "PAYSTAGE_POLICY_PATH": "/absolute/path/to/policy.json",
        "PAYSTAGE_RPC_URL": "https://mainnet.base.org"
      }
    }
  }
}

Using a local npm install

{
  "mcpServers": {
    "paystage": {
      "command": "node",
      "args": ["./node_modules/@paystage/mcp/dist/cli.js"],
      "env": {
        "PAYSTAGE_POLICY_PATH": "/absolute/path/to/policy.json",
        "PAYSTAGE_RPC_URL": "https://mainnet.base.org"
      }
    }
  }
}

PAYSTAGE_POLICY_PATH (required): path to your local policy.json.
PAYSTAGE_RPC_URL (optional): RPC endpoint used by on-chain checks. Defaults to a public Base RPC.

Tools

Tool	Status	What it does
`evaluate_mcp_payment`	Available now	Evaluates a proposed x402 payment against the local policy and returns `pay`, `review`, or `do_not_pay`.
`list_outstanding_auths`	Available now	Lists payments that are authorized but not yet settled.
`evaluate_outstanding_auths`	Available now	Evaluates outstanding authorizations and flags double-pay or limbo risk.
`evaluate_hip3_trade`	Available now	Evaluates a proposed HIP-3 / trade.xyz order against a local TradePolicy (`allow` \| `review` \| `do_not_trade`). Not financial advice — local policy gate only.
`evaluate_velocity`	Available now	Rate and spend-pattern velocity checks against the local policy.

Packages

Package	Role	Links
`@paystage/mcp`	Umbrella MCP server (start here)	npm
`@paystage/preflight`	MCP payment preflight	npm
`@paystage/auth-watch`	Outstanding-auth watch	npm
`@paystage/policy`	Policy parsing and evaluation	npm
`@paystage/trade-preflight`	HIP-3 / trade.xyz trade preflight	npm

Development

This is a monorepo.

pnpm install
pnpm build
pnpm test
pnpm lint

Contributing

PayStage is built in the open, and outside contributions are welcome.

Add a drainer address. Open a PR adding it to KNOWN_DRAINERS.md with a public source link (incident report, explorer label, or security write-up). Unsourced addresses won't be merged.
Add an integration example. LangChain, AgentKit, ElizaOS and others are all welcome.
Report a bypass. If an unsafe payment gets past preflight, open an issue. That's the most valuable contribution there is.

Look for issues labelled good first issue to get started.

License

MIT

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4.8

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