vet/docs/mcp.md

vet MCP Server

The vet MCP server is designed to run locally using stdio or sse transports. It provides tools for MCP clients such as Claude Code, Cursor and others to vet open source packages before they are used in a project through AI generated code.

vet MCP server can protect against Slopsquatting attacks, malicious packages, vulnerabilities and other security risks.

Supported Ecosystems

vet MCP server currently supports the following ecosystems:

• npm
• PyPI

Usage

Start the MCP server using SSE transport:

vet server mcp --server-type sse

Start the MCP server using stdio transport:

vet -s -l /tmp/vet-mcp.log server mcp --server-type stdio

Avoid using stdout logging as it will interfere with the MCP server output.

SSE Transport Features

The SSE (Server-Sent Events) transport supports:

• GET requests: For establishing SSE connections to receive real-time events
• HEAD requests: For endpoint health checks and capability probing (useful for tools like Langchain)
• POST requests: For sending messages to the MCP server via the message endpoint

The SSE endpoint returns appropriate headers for HEAD requests without a body, allowing tools to verify endpoint availability and capabilities.

Security: Host and Origin Guards

For SSE, the server enforces simple, user-configurable guards to reduce the risk of unauthorized cross-origin access and DNS rebinding attacks.

• Host guard: Only allows connections whose Host header matches an allowed host list.
• Origin guard: For browser requests, only allows requests whose Origin starts with an allowed prefix.

These checks are on by default with sensible localhost defaults, and you can customize them with flags when starting the server.

Defaults

• Allowed hosts: localhost:9988, 127.0.0.1:9988, [::1]:9988
• Allowed origin prefixes: http://localhost:, http://127.0.0.1:, https://localhost:

Requests that fail the host check are rejected with status 403, and requests that fail the origin check are rejected with status 403.

Customize allowed hosts and origins

You can override the defaults using the following flags:

vet server mcp \
  --server-type sse \
  --sse-allowed-hosts "localhost:8080,127.0.0.1:8080" \
  --sse-allowed-origins "http://localhost:,https://localhost:"

If you are running behind a proxy or using a different port, set both lists to match your environment. For example, when exposing SSE on port 3001:

vet server mcp \
  --server-type sse \
  --sse-allowed-hosts "localhost:3001,127.0.0.1:3001" \
  --sse-allowed-origins "http://localhost:,http://127.0.0.1:,https://localhost:"

With Docker, append the same flags to the container command:

docker run --rm -i ghcr.io/safedep/vet:latest \
  server mcp \
  --server-type sse \
  --sse-allowed-hosts "localhost:9988,127.0.0.1:9988" \
  --sse-allowed-origins "http://localhost:,http://127.0.0.1:,https://localhost:"

Tip: Non-browser clients may omit the Origin header. Those requests are allowed as long as the host guard passes.

Configure MCP Client

Note: The example below uses pre-build docker image. You can build your own by running docker build -t ghcr.io/safedep/vet:latest .

Add following configuration to your MCP client configuration file:

"vet-mcp": {
  "command": "docker",
  "args": [
    "run",
    "--rm",
    "-i",
    "ghcr.io/safedep/vet:latest",
    "-l",
    "/tmp/vet-mcp.log",
    "server",
    "mcp"
  ]
}

vet uses stdio by default, if you wish to use SSE transport, add following args: "--server-type", "sse"

Note: While docker containers can help keep the MCP server process isolated, it needs to be periodically updated to the latest version.

Alternatively, you can use vet binary directly as an MCP server using stdio transport. Use the following command to start the MCP server:

vet -l /tmp/vet-mcp.log server mcp --server-type stdio

Configure IDE

Cursor

Add vet-mcp server to either .cursor/mcp.json (project specific configuration) or ~/.cursor/mcp.json (applies to all projects)

{
  "mcpServers": {
    "vet-mcp": {
      "command": "docker",
      "args": [
        "run",
        "--rm",
        "-i",
        "ghcr.io/safedep/vet:latest",
        "-l",
        "/tmp/vet-mcp.log",
        "server",
        "mcp"
      ]
    }
  }
}

Add the following to .cursor/rules/vet-mcp.mdc file:

---
description: vet Open Source Packages using vet MCP server
alwaysApply: true
---

Always use vet-mcp to vet any open source library package suggested by AI generated code before installation.
Follow the rules below to use vet-mcp:

- Try to find the latest version. If not found, it is likely a slopsquatting vulnerability
- Always check for critical vulnerabilities and malware

Example usage with Cursor:

📄 Cursor MCP server reference

Visual Studio Code

Add vet-mcp server to .vscode/mcp.json (project specific configuration)

{
  "servers": {
    "vet-mcp": {
      "command": "docker",
      "args": [
        "run",
        "--rm",
        "-i",
        "ghcr.io/safedep/vet:latest",
        "-l",
        "/tmp/vet-mcp.log",
        "server",
        "mcp"
      ]
    }
  }
}

In order to use vet-mcp for all projects in Visual Studio Code, add following mcp setting in Visual Studio Code User Settings (settings.json)

{
  "mcp": {
    "servers": {
      "vet-mcp": {
        "command": "docker",
        "args": [
          "run",
          "--rm",
          "-i",
          "ghcr.io/safedep/vet:latest",
          "-l",
          "/tmp/vet-mcp.log",
          "server",
          "mcp"
        ]
      }
    }
  }
}

Add the following to .github/copilot-instructions.md file:

Always use vet-mcp to vet any open source library package suggested by AI generated code before installation.
Follow the rules below to use vet-mcp:

- Try to find the latest version. If not found, it is likely a slopsquatting vulnerability
- Always check for critical vulnerabilities and malware

Example usage with Visual Studio Code:

📄 Visual Studio Code MCP server reference

Claude Code

Add the following to .mcp.json in your Claude Code project:

{
  "mcpServers": {
    "vet-mcp": {
      "command": "docker",
      "args": [
        "run",
        "--rm",
        "-i",
        "ghcr.io/safedep/vet:latest",
        "server",
        "mcp"
      ]
    }
  }
}

Note: You can also use vet binary directly as an MCP server using stdio transport.