Which integrations are available for this server?

Enables integration with Express.js web applications, providing examples for implementing rate-limited endpoints, cached responses, and request handling with the MCP utilities. Supports testing with Jest, including test structure, coverage reporting, and pattern-based test filtering for MCP server components. Includes Kubernetes-compatible storage size formatting utilities for displaying resource metrics in standardized formats (e.g., Mi, Gi). Available as an NPM package with installation instructions and dependency management for integrating MCP utilities into projects. Built with TypeScript support, providing type-safe interfaces, error checking, and enhanced development experience for MCP server implementations. Integrates with Zod schema validation for type-safe argument validation, resource operations, and structured data handling in MCP tools.

How do I use MCP Utils?

1. Click on "Install Server". 2. Wait a few minutes for the server to deploy. Once ready, it will show a "Started" state. 3. In the chat, type @ followed by the MCP server name and your instructions, e.g., "@MCP Utils format this JSON response with proper table formatting" That's it! The server will respond to your query, and you can continue using it as needed. Here is a step-by-step guide with screenshots.

@haakco/mcp-utils

Comprehensive shared utilities library for MCP (Model Context Protocol) servers

Eliminates code duplication and provides standardized, production-ready utilities for building robust MCP servers.

Tests TypeScript Lint

Installation

npm install @haakco/mcp-utils

Related MCP server: MCP TypeScript SDK

Quick Start

import { 
  BaseToolHandler, 
  ResponseBuilder, 
  createTextResponse,
  formatSuccess,
  createLogger
} from '@haakco/mcp-utils';

class MyMCPServer extends BaseToolHandler {
  private logger = createLogger('my-server');

  async handleTool(args: unknown) {
    try {
      const result = await this.performOperation(args);
      this.logger.info('Operation completed successfully');
      return createTextResponse(formatSuccess(result));
    } catch (error) {
      this.logger.error('Operation failed:', error);
      return createErrorResponse(error);
    }
  }
}

🚀 Core Features

🏗️ MCP Architecture Components

BaseToolHandler - Standardized tool execution patterns
ResponseBuilder - Consistent MCP response formatting
InstanceManager - Multi-instance server support
ToolRegistry - Tool registration and management

🎨 Formatting & Presentation

Message Formatters - ✅ ❌ ⚠️ ℹ️ status indicators
Size Formatters - Bytes, storage units (KB, MB, GB, Ki, Mi, Gi)
Table Formatters - Structured data presentation
JSON/Text Utilities - Safe serialization and truncation

📅 DateTime Operations

Duration Formatting - Human-readable time spans
Age Calculation - "2 hours ago", "3 days old"
Relative Time - "in 5 minutes", "1 week ago"
Duration Parsing - "1h30m" → milliseconds

🧠 Advanced Caching

SimpleCache - TTL-based caching
LRUCache - Least Recently Used eviction
TTLCache - Combined TTL + LRU strategies
DebouncedCache - Batched operation caching
Memoization - Function result caching

🚦 Rate Limiting

Token Bucket - Burst capacity with refill
Sliding Window - Rolling time-based limits
Fixed Window - Period-based rate limiting
Leaky Bucket - Smooth rate control
Multi-Tier - Multiple simultaneous limits
Keyed Limiters - Per-user/per-resource limits

🔌 WebSocket Utilities

ReconnectingWebSocket - Auto-reconnection with backoff
Message Router - Type-based message handling
RPC Client - Request/response over WebSocket
Connection Pool - Managed connection lifecycle

📊 Logging & Monitoring

Structured Logging - Context-aware log entries
Performance Timing - Operation duration tracking
Environment-based - Debug/production configurations
Multiple Outputs - Console, silent, custom loggers

📚 API Reference

Core MCP Utilities

Response Creation

import { createTextResponse, createErrorResponse, createSuccessResponse } from '@haakco/mcp-utils';

// Basic responses
createTextResponse('Operation completed');
createErrorResponse(new Error('Failed to connect'));
createSuccessResponse('User created successfully');

// Multi-part responses
createMultipartResponse(['Header', 'Content', 'Footer']);

// Progress indicators
createProgressResponse(75, 100, 'Processing data');

Argument Validation

import { validateToolArgs, validateRequiredArgs, extractPagination } from '@haakco/mcp-utils';

// Schema validation
const args = validateToolArgs(input, (data) => userSchema.parse(data), 'create_user');

// Required field validation
const validated = validateRequiredArgs(input, ['name', 'email'], 'User creation');

// Pagination extraction
const { page, perPage, offset, limit } = extractPagination(args);

Formatting Utilities

Message Formatting

import { formatSuccess, formatError, formatWarning, formatInfo } from '@haakco/mcp-utils';

formatSuccess('Operation completed'); // ✅ Operation completed
formatError('Connection failed');     // ❌ Error: Connection failed
formatWarning('Low disk space');      // ⚠️ Warning: Low disk space
formatInfo('System status');          // ℹ️ System status

Size & Number Formatting

import { formatBytes, formatStorageSize, formatPercentage, formatCPU } from '@haakco/mcp-utils';

formatBytes(1048576);          // 1 MB
formatStorageSize(1048576);    // 1Mi (Kubernetes format)
formatPercentage(75, 100);     // 75.00%
formatCPU(0.75);              // 75.00%

Table & List Formatting

import { formatTable, formatSimpleTable, formatList, formatBulletList } from '@haakco/mcp-utils';

// Object array to table
const data = [
  { name: 'John', age: 30, city: 'NYC' },
  { name: 'Jane', age: 25, city: 'LA' }
];
formatTable(data);
// name | age | city
// -----|-----|-----
// John | 30  | NYC
// Jane | 25  | LA

// Key-value table
formatSimpleTable({ name: 'Server1', status: 'Running', cpu: '45%' });
// name   : Server1
// status : Running
// cpu    : 45%

// Lists
formatList(['item1', 'item2', 'item3'], ' | ');        // item1 | item2 | item3
formatBulletList(['item1', 'item2']);                   // • item1\n• item2

DateTime Utilities

Duration Formatting

import { formatDuration, formatDurationFromSeconds, formatAge } from '@haakco/mcp-utils';

formatDuration(90061000);           // 1d 1h 1m 1s
formatDurationFromSeconds(3661);    // 1h 1m 1s
formatAge(Date.now() - 3600000);    // 1h (age from timestamp)

Relative Time

import { formatRelativeTime, parseDuration } from '@haakco/mcp-utils';

formatRelativeTime(new Date(Date.now() - 3600000)); // 1 hour ago
formatRelativeTime(new Date(Date.now() + 1800000)); // in 30 minutes

parseDuration('1h30m');     // 5400000 (milliseconds)
parseDuration('2d12h');     // 216000000

Caching System

Simple TTL Cache

import { SimpleCache } from '@haakco/mcp-utils';

const cache = new SimpleCache<string>(60000); // 1 minute TTL

cache.set('key1', 'value1');
cache.get('key1');          // 'value1'
cache.has('key1');          // true

// Custom TTL for specific items
cache.set('key2', 'value2', 30000); // 30 second TTL

LRU Cache

import { LRUCache } from '@haakco/mcp-utils';

const cache = new LRUCache<string>(100); // Max 100 items

cache.set('key1', 'value1');
cache.get('key1');          // Marks as recently used
cache.size();               // Current cache size

Combined TTL + LRU Cache

import { TTLCache } from '@haakco/mcp-utils';

const cache = new TTLCache<string>({
  ttl: 300000,      // 5 minutes
  maxSize: 1000,    // Max 1000 items
  onEvict: (key, value) => console.log(`Evicted ${key}`)
});

cache.set('key1', 'value1');
cache.cleanup();            // Manual cleanup of expired items

Function Memoization

import { memoize } from '@haakco/mcp-utils';

const expensiveOperation = async (id: string) => {
  // Expensive API call or computation
  return await fetch(`/api/data/${id}`).then(r => r.json());
};

const memoized = memoize(expensiveOperation, {
  ttl: 300000,     // 5 minute cache
  keyGenerator: (id) => `data:${id}`
});

// First call - executes function
await memoized('user1');  

// Second call - returns cached result
await memoized('user1');

Rate Limiting

Token Bucket Rate Limiter

import { TokenBucketRateLimiter } from '@haakco/mcp-utils';

const limiter = new TokenBucketRateLimiter(
  10,     // Bucket capacity (max burst)
  2       // Refill rate (tokens per second)
);

// Try to acquire tokens
if (await limiter.acquire(1)) {
  // Request allowed
  await processRequest();
}

// Wait until tokens available
await limiter.acquireOrWait(1);

Sliding Window Rate Limiter

import { SlidingWindowRateLimiter } from '@haakco/mcp-utils';

const limiter = new SlidingWindowRateLimiter(
  60000,  // 1 minute window
  100     // Max 100 requests per window
);

if (await limiter.acquire()) {
  // Request allowed
} else {
  const waitTime = limiter.getTimeUntilNextRequest();
  console.log(`Rate limited. Wait ${waitTime}ms`);
}

Multi-Tier Rate Limiting

import { MultiTierRateLimiter } from '@haakco/mcp-utils';

const limiter = new MultiTierRateLimiter([
  { windowMs: 1000, maxRequests: 10, name: 'per-second' },
  { windowMs: 60000, maxRequests: 100, name: 'per-minute' },
  { windowMs: 3600000, maxRequests: 1000, name: 'per-hour' }
]);

const result = await limiter.acquire();
if (!result.allowed) {
  console.log(`Limited by: ${result.limitedBy}`);
}

Rate-Limited Functions

import { rateLimitFunction, debounce, throttle } from '@haakco/mcp-utils';

// Rate-limited function wrapper
const limitedAPI = rateLimitFunction(apiCall, {
  requestsPerSecond: 5,
  burst: 10
});

// Debounced function (delays execution)
const debouncedSave = debounce(saveData, 1000);

// Throttled function (limits execution frequency)
const throttledUpdate = throttle(updateUI, 100);

WebSocket Utilities

Reconnecting WebSocket

import { ReconnectingWebSocket } from '@haakco/mcp-utils';

const ws = new ReconnectingWebSocket({
  url: 'wss://api.example.com/ws',
  maxReconnectAttempts: 5,
  reconnectInterval: 5000,
  reconnectBackoff: 1.5,
  pingInterval: 30000
});

ws.on('open', () => console.log('Connected'));
ws.on('message', (data) => console.log('Received:', data));
ws.on('reconnecting', (attempt) => console.log(`Reconnecting... attempt ${attempt}`));

ws.send({ type: 'subscribe', channel: 'updates' });

Message Router

import { WebSocketRouter } from '@haakco/mcp-utils';

const router = new WebSocketRouter<{ type: string; payload?: any }>();

router.on('user.created', async (message) => {
  console.log('New user:', message.payload);
});

router.on('notification', async (message) => {
  await showNotification(message.payload);
});

router.setDefaultHandler((message) => {
  console.log('Unhandled message:', message);
});

// Handle incoming messages
ws.on('message', (data) => router.handle(data));

WebSocket RPC

import { WebSocketRPC } from '@haakco/mcp-utils';

const rpc = new WebSocketRPC(ws, {
  timeout: 30000,
  idGenerator: () => `req-${Date.now()}`
});

// Make RPC calls
const user = await rpc.call('getUser', { id: '123' });
const result = await rpc.call('updateProfile', { name: 'New Name' });

Logging System

Basic Logger

import { createLogger, createStructuredLogger } from '@haakco/mcp-utils';

const logger = createLogger('my-module');

logger.info('Application started');
logger.warn('Low memory warning');
logger.error('Database connection failed');
logger.debug('Debug information');

Structured Logger with Context

const logger = createStructuredLogger('api', 'app', {
  service: 'user-service',
  version: '1.2.3'
});

logger.info('User login successful');
// Output: INFO: User login successful [{"service":"user-service","version":"1.2.3"}]

// Add context for child logger
const requestLogger = logger.child({ requestId: 'req-123', userId: 'user-456' });
requestLogger.info('Processing request');

Performance Logger

import { createPerformanceLogger } from '@haakco/mcp-utils';

const perfLogger = createPerformanceLogger('performance');

// Manual timing
perfLogger.start('database-query');
await queryDatabase();
perfLogger.end('database-query', { query: 'SELECT * FROM users' });

// Automatic timing
const result = await perfLogger.measure(
  'api-call',
  () => fetch('/api/data').then(r => r.json()),
  { endpoint: '/api/data' }
);

Environment-based Logger

import { createLoggerFromEnv, LogLevel, createLevelLogger } from '@haakco/mcp-utils';

// Automatically configures based on DEBUG and LOG_LEVEL env vars
const logger = createLoggerFromEnv('my-app');

// Or explicit level configuration
const logger = createLevelLogger('my-app', LogLevel.INFO);

🏗️ Advanced Usage

Custom Tool Handler

import { BaseToolHandler, createTextResponse, formatSuccess } from '@haakco/mcp-utils';
import { z } from 'zod';

class CustomToolHandler extends BaseToolHandler {
  constructor() {
    super('my-custom-server');
  }

  getTools() {
    return [
      this.createTool(
        'process_data',
        'Process data with validation and formatting',
        z.object({
          data: z.array(z.string()),
          format: z.enum(['json', 'table', 'list']).default('json')
        }),
        async (args) => {
          const processed = await this.processData(args.data);
          
          switch (args.format) {
            case 'table':
              return createTextResponse(formatTable(processed));
            case 'list':
              return createTextResponse(formatBulletList(processed.map(String)));
            default:
              return createTextResponse(formatSuccess(JSON.stringify(processed)));
          }
        }
      )
    ];
  }

  private async processData(data: string[]): Promise<any[]> {
    // Your custom processing logic
    return data.map(item => ({ original: item, processed: item.toUpperCase() }));
  }
}

Batch Response Builder

import { BatchResponseBuilder } from '@haakco/mcp-utils';

const response = new BatchResponseBuilder()
  .addSuccess('Connection established')
  .addInfo('Processing 150 items')
  .addSeparator()
  .add('Results:')
  .addSuccess('Created 145 items')
  .addWarning('Skipped 3 duplicates')
  .addError('Failed to create 2 items')
  .addEmptyLine()
  .addInfo('Operation completed in 2.3 seconds')
  .build();

return response; // Returns proper CallToolResult

Resource Operation Mixin

import { ResourceOperationMixin } from '@haakco/mcp-utils';
import { z } from 'zod';

interface User {
  id: string;
  name: string;
  email: string;
}

class UserTools extends ResourceOperationMixin<User> {
  constructor(private userClient: UserClient) {
    super('user-management');
  }

  getTools() {
    return this.createResourceTools({
      resourceName: 'User',
      client: this.userClient,
      formatItem: (user) => `${user.name} <${user.email}>`,
      validateCreate: z.object({
        name: z.string().min(1),
        email: z.string().email()
      }),
      validateUpdate: z.object({
        name: z.string().min(1).optional(),
        email: z.string().email().optional()
      })
    });
  }
}

📦 Integration Examples

Express.js Integration

import express from 'express';
import { createLogger, rateLimitFunction, SimpleCache } from '@haakco/mcp-utils';

const app = express();
const logger = createLogger('api-server');
const cache = new SimpleCache<any>(300000); // 5 minute cache

// Rate-limited endpoint
const rateLimitedHandler = rateLimitFunction(
  async (req, res) => {
    const data = await fetchData(req.params.id);
    res.json(data);
  },
  { requestsPerSecond: 10, burst: 20 }
);

app.get('/api/data/:id', async (req, res) => {
  const cached = cache.get(req.params.id);
  if (cached) {
    logger.info('Cache hit', { id: req.params.id });
    return res.json(cached);
  }

  await rateLimitedHandler(req, res);
});

WebSocket Server Integration

import WebSocket from 'ws';
import { WebSocketRouter, createLogger, TokenBucketRateLimiter } from '@haakco/mcp-utils';

const logger = createLogger('ws-server');
const rateLimiter = new TokenBucketRateLimiter(10, 1); // 10 burst, 1/sec refill

const wss = new WebSocket.Server({ port: 8080 });

wss.on('connection', (ws) => {
  const router = new WebSocketRouter();
  
  router.on('message', async (data) => {
    if (await rateLimiter.acquire()) {
      await handleMessage(data);
    } else {
      ws.send(JSON.stringify({ error: 'Rate limit exceeded' }));
    }
  });

  ws.on('message', (data) => {
    try {
      const message = JSON.parse(data.toString());
      router.handle(message);
    } catch (error) {
      logger.error('Invalid message format', error);
    }
  });
});

🧪 Testing

The library includes comprehensive test coverage (85/85 tests passing):

# Run all tests
npm test

# Run tests with coverage
npm run test:coverage

# Run specific test suites
npm test -- --testNamePattern="Cache"
npm test -- --testNamePattern="Rate.*Limiter"

Test Structure

tests/
├── base-handler.test.ts      # Core MCP functionality
├── cache.test.ts            # All caching strategies
├── datetime.test.ts         # DateTime utilities
├── formatters.test.ts       # Formatting functions
├── response-builder.test.ts # Response building
├── task-helpers.test.ts     # Task execution
└── validators.test.ts       # Validation utilities

🚀 Development

# Install dependencies
npm install

# Run tests in watch mode
npm run test:watch

# Build the library
npm run build

# Lint and format code
npm run lint
npm run lint:fix

# Type checking
npm run type-check

📄 License

MIT License - see LICENSE file for details.

🤝 Contributing

Fork the repository
Create a feature branch
Make your changes with tests
Ensure all tests pass and linting is clean
Submit a pull request

Built with TypeScript, tested with Jest, and designed for production MCP servers.