mcplog

Small JSON-lines logger for MCP servers.

Install

pnpm add mcplog
# or
npm install mcplog

Usage

import { McpLogger } from "mcplog";

Usage

import { McpLogger } from "mcp-log";

const logger = new McpLogger({ name: "my-mcp-server" });

logger.info("server started", { port: 3000 });
logger.error("request failed", { requestId: "abc123" });

Logs are written to stderr by default so MCP protocol messages on stdout stay untouched. Set CLANKER_LOG_FILE or pass filePath to write JSON lines to a file instead.

API

new McpLogger({
  name: string,
  level?: "debug" | "info" | "warn" | "error",
  filePath?: string,
  stderr?: { write(chunk: string): unknown },
})

Methods: debug, info, warn, and error.

The package also exports the LogLevel and LogSink types.