servers-modelcontextprotocol/src/everything/tools/toggle-simulated-logging.ts

import { McpServer } from "@modelcontextprotocol/sdk/server/mcp.js";
import { CallToolResult } from "@modelcontextprotocol/sdk/types.js";
import {
  beginSimulatedLogging,
  stopSimulatedLogging,
} from "../server/logging.js";

// Tool configuration
const name = "toggle-simulated-logging";
const config = {
  title: "Toggle Simulated Logging",
  description: "Toggles simulated, random-leveled logging on or off.",
  inputSchema: {},
};

// Track enabled clients by session id
const clients: Set<string | undefined> = new Set<string | undefined>();

/**
 * Registers the `toggle-simulated-logging` tool with the provided MCP server.
 *
 * The registered tool enables or disables the sending of periodic, random-leveled
 * logging messages the connected client.
 *
 * When invoked, it either starts or stops simulated logging based on the session's
 * current state. If logging for the specified session is active, it will be stopped;
 * if it is inactive, logging will be started.
 *
 * @param {McpServer} server - The server instance to which the tool is registered.
 */
export const registerToggleSimulatedLoggingTool = (server: McpServer) => {
  server.registerTool(
    name,
    config,
    async (_args, extra): Promise<CallToolResult> => {
      const sessionId = extra?.sessionId;

      let response: string;
      if (clients.has(sessionId)) {
        stopSimulatedLogging(sessionId);
        clients.delete(sessionId);
        response = `Stopped simulated logging for session ${sessionId}`;
      } else {
        beginSimulatedLogging(server, sessionId);
        clients.add(sessionId);
        response = `Started simulated, random-leveled logging for session ${sessionId} at a 5 second pace. Client's selected logging level will be respected. If an interval elapses and the message to be sent is below the selected level, it will not be sent. Thus at higher chosen logging levels, messages should arrive further apart. `;
      }

      return {
        content: [{ type: "text", text: `${response}` }],
      };
    }
  );
};