MCP Server Logger

console.log for your stdio MCP server

Why?

When developing an MCP (Model Context Protocol) server with stdio transport, console.log interferes with the protocol communication.

For example, this is what you normally get in MCP inspector npx @modelcontextprotocol/inspector when calling console.log in your MCP server code:

Error from MCP server: SyntaxError: Unexpected token S in JSON at position 0

Solution

This package patches the console methods (log, warn, error, debug) and redirects logs to a separate terminal.

https://github.com/user-attachments/assets/33ff367e-74b4-48e8-9f04-0bcafbad5e00

Usage

Start the logger in a terminal where you want to see the logs:

npx mcps-logger

Install the logger in your MCP server:

npm install mcps-logger

Add it to your MCP server entry file:

import "mcps-logger/console";

Or if you want to use in development mode only:

if (process.env.NODE_ENV !== "production") {
    import("mcps-logger/console");
}