MCP Output Firewall

MCP Output Firewall runs locally from a Node.js package published to the npm registry: mcp-output-firewall version 0.3.0. It speaks MCP over stdio, so the client starts it as a program and talks to it through standard input and output. It needs Node.js; clients usually start it with npx — the usual command is npx -y mcp-output-firewall@0.3.0.

In the mcpServers JSON format that many desktop and editor MCP clients read, the entry looks like this (placeholders in angle brackets):

{
  "mcpServers": {
    "mcp-output-firewall": {
      "command": "npx",
      "args": [
        "-y",
        "mcp-output-firewall@0.3.0"
      ]
    }
  }
}

Derived from the registry entry, not tested here. What the server does, and on what terms, is set by its publisher; check its repository or website before giving it access to your accounts or files. How to add an MCP server to an assistant · Before you connect