logger()

Logs tool calls with execution time.

Import

import { logger } from "@lynq/lynq/logger";

Usage

server.use(logger());

Options

Option	Type	Default	Description
log	(message: string) => void	console.log	Custom log function

Example

import { createMCPServer, text } from "@lynq/lynq";
import { logger } from "@lynq/lynq/logger";

const server = createMCPServer({ name: "my-app", version: "1.0.0" });

// Apply globally to all tools
server.use(logger());

// Or use a custom log function
server.use(logger({ log: (msg) => fs.appendFileSync("mcp.log", msg + "\n") }));

server.tool(
  "greet",
  { description: "Say hello" },
  async (c) => text(`Hello, ${c.params.name}!`),
);

Output:

[greet] called (session: abc123)
[greet] 4.2ms

On error:

[greet] called (session: abc123)
[greet] 12.5ms ERROR

Under the hood

Uses the onCall hook. Records performance.now() before calling next(), then logs the tool name, elapsed time, and whether the result has isError set. Since it wraps next(), it measures the full execution time including any downstream middleware and the handler itself.