Nestjs MCP Server Module Xtd

🚀 Creating MCP Server Module with NestJS

This is a NestJS module for creating a Model Context Protocol (MCP) server that supports Server-Sent Events (SSE) transmission. It aims to simplify the process of building MCP servers and provides a set of features to enhance functionality and security.

✨ Features

• 🚀 SSE transmission for streaming and tool execution.
• 🔍 Automatic discovery and registration of tool and resource.
• 💯 Zod-based request validation.
• 📊 Progress notification.
• 🔒 Guard-based authentication.

📦 Installation

npm install @rekog/mcp-nest @modelcontextprotocol/sdk zod

🚀 Quick Start

1. Import the Module

// app.module.ts
import { Module } from '@nestjs/common';
import { McpModule } from '@rekog/mcp-nest';
import { GreetingTool } from './greeting.tool';

@Module({
  imports: [
    McpModule.forRoot({
      name: 'my-mcp-server',
      version: '1.0.0',
    }),
  ],
  providers: [GreetingTool],
})
export class AppModule {}

2. Define Tools and Resources

// greeting.tool.ts
import { Injectable } from '@nestjs/common';
import { Tool, Context } from '@rekog/mcp-nest';
import { z } from 'zod';
import { Progress } from '@modelcontextprotocol/sdk/types';

@Injectable()
export class GreetingTool {
  constructor() {}

  @Tool({
    name: 'hello-world',
    description:
      'Returns a greeting and simulates a long operation with progress updates',
    parameters: z.object({
      name: z.string().default('World'),
    }),
  })
  async sayHello({ name }, context: Context) {
    const greeting = `Hello, ${name}!`;

    const totalSteps = 5;
    for (let i = 0; i < totalSteps; i++) {
      await new Promise((resolve) => setTimeout(resolve, 500));

      // Send progress updates.
      await context.reportProgress({
        progress: (i + 1) * 20,
        total: 100,
      } as Progress);
    }

    return {
      content: [{ type: 'text', text: greeting }],
    };
  }

  @Resource({
    uri: 'mcp://hello-world/{userName}',
    name: 'Hello World',
    description: 'A simple greeting resource',
    mimeType: 'text/plain',
  })
  // Different from the SDK, we put parameters and URI in the same object.
  async getCurrentSchema({ uri, userName }) {
    return {
      content: [
        {
          uri,
          text: `User is ${userName}`,
          mimeType: 'text/plain',
        },
      ],
    };
  }
}

You're all set!

📚 Documentation

API Endpoints

• GET /sse: SSE connection endpoint (protected by Guard if configured).
• POST /messages: Tool execution endpoint (protected by Guard if configured).

💡 Usage Tip

You can exclude these endpoints using a global prefix, but the recommended way is:

app.setGlobalPrefix('/api', { exclude: ['sse', 'messages'] });

Authentication

You can use standard NestJS Guards to protect MCP endpoints.

1. Create a Guard

Implement the CanActivate interface. This guard should handle request validation (e.g., checking JWT, API keys) and optionally attach user information to the request object. It's the same as in the NestJS documentation.

2. Apply the Guard

Pass your guard to the McpModule.forRoot configuration. This guard will be applied to the /sse and /messages endpoints.

// app.module.ts
import { Module } from '@nestjs/common';
import { McpModule } from '@rekog/mcp-nest';
import { GreetingTool } from './greeting.tool';
import { AuthGuard } from './auth.guard';

@Module({
  imports: [
    McpModule.forRoot({
      name: 'my-mcp-server',
      version: '1.0.0',
      guards: [AuthGuard], // Apply the guard here
    }),
  ],
  providers: [GreetingTool, AuthGuard], // Make sure the guard is also provided
})
export class AppModule {}

That's it! The rest is the same as NestJS Guards.