MCP Nest

What is MCP Nest about?

MCP Nest provides a NestJS module that enables developers to define and expose AI tools, resources, and prompt templates as MCP endpoints, leveraging NestJS's dependency injection and guard system.

How to use MCP Nest?

1. Install the package with npm (or npx for quick install):

   npm install @rekog/mcp-nest @modelcontextprotocol/sdk zod@^3
   

2. Import the module in your NestJS AppModule using McpModule.forRoot({ name: 'my-mcp-server', version: '1.0.0' }).
3. Create Injectable classes and annotate methods with @Tool (or define resources and prompts) to expose them via MCP.
4. Run the NestJS application as usual; the MCP server will be available over the configured transports (HTTP+SSE, streamable HTTP, STDIO).

Key Features of MCP Nest

• Multi‑transport support: HTTP+SSE, streamable HTTP, STDIO.
• Automatic tool discovery with Zod schema validation.
• Interactive tool calls with elicitation and progress notifications.
• Full request context access inside tool handlers.
• Resource serving and dynamic resource templates.
• Reusable prompt templates.
• Guard‑based authentication (OAuth) and optional built‑in authorization server (beta).
• Seamless integration with NestJS dependency injection.

Use Cases of MCP Nest

• Building enterprise‑grade AI assistants that need to call backend services safely.
• Exposing internal business logic as AI‑callable tools (e.g., CRM lookups, data transformations).
• Serving static or dynamic AI‑consumable resources such as documents or datasets.
• Creating reusable prompt libraries for consistent LLM interactions across teams.
• Deploying AI‑enabled microservices with built‑in security via NestJS guards.

FAQ from MCP Nest

Q: Do I need a separate server to run MCP? A: No. The MCP server runs inside your existing NestJS application.

Q: Which transports are supported? A: HTTP with Server‑Sent Events, streamable HTTP responses, and STDIO for CLI‑based usage.

Q: How is authentication handled? A: Use NestJS guards; the module also offers a built‑in OAuth authorization server (beta) or can integrate with external providers like Keycloak or Auth0.

Q: Can I use TypeORM with the built‑in auth server? A: Yes, install @nestjs/typeorm and typeorm as optional peer dependencies.

Q: How are tool parameters validated? A: Define Zod schemas in the @Tool decorator; validation occurs automatically before the method is invoked.

NestJS MCP Server Module

A NestJS module to effortlessly expose tools, resources, and prompts for AI, from your NestJS applications using the Model Context Protocol (MCP).

With @rekog/mcp-nest you define tools, resources, and prompts in a way that's familiar in NestJS and leverage the full power of dependency injection to utilize your existing codebase in building complex enterprise ready MCP servers.

Features

• 🚀 Multi-Transport Support: HTTP+SSE, Streamable HTTP, and STDIO
• 🔧 Tools: Expose NestJS methods as MCP tools with automatic discovery and Zod validation
  • 🛠️ Elicitation: Interactive tool calls with user input elicitation
  • 📊 Progress Notifications: Real-time progress updates for long-running operations
  • 🌐 HTTP Request Access: Full access to request context within MCP handlers
• 📁 Resources: Serve content and data through MCP resource system
• 📚 Resource Templates: Dynamic resources with parameterized URIs
• 💬 Prompts: Define reusable prompt templates for AI interactions
• 🔐 Guard-based Authentication: Guard-based security with OAuth support
• 🏠 Built-in Authorization Server — Using the built-in Authorization Server for easy setups. (Beta)
• 🌐 External Authorization Server — Securing your MCP server with an external authorization server (Keycloak, Auth0, etc).
• 💉 Dependency Injection: Leverage NestJS DI system throughout MCP components

Are you interested to build ChatGPT widgets (with the OpenAI SDK)? Find out how to do that with @rekog/MCP-Nest in this repository MCP-Nest-Samples/pizzaz-openai-apps-sdk

Installation

npm install @rekog/mcp-nest @modelcontextprotocol/sdk zod@^3

Optional dependencies

If you use the built-in authorization server with the TypeORM store, install the following optional peer dependencies:

npm install @nestjs/typeorm typeorm

Quick Start

// 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 {}

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

@Injectable()
export class GreetingTool {
  @Tool({
    name: 'greeting-tool',
    description: 'Returns a greeting with progress updates',
    parameters: z.object({
      name: z.string().default('World'),
    }),
  })
  async sayHello({ name }, context: Context) {
    await context.reportProgress({ progress: 50, total: 100 });
    return `Hello, ${name}!`;
  }
}

Documentation

• Tools Guide - Define and expose NestJS methods as MCP tools
• Resources Guide - Serve static and dynamic content
• Resource Templates Guide - Create parameterized resources
• Prompts Guide - Build reusable prompt templates
• Built-in Authorization Server - Secure your MCP server with built-in OAuth
• External Authorization Server - Securing your MCP server with an external authorization server (Keycloak, Auth0, etc)
• Server examples - MCP servers examples (Streamable HTTP, HTTP, and STDIO) and with Fastify support

Playground

The playground directory contains working examples for all features. Refer to playground/README.md for details.