-
security-
license-
qualityA demonstration server that implements the Model Context Protocol (MCP) SDK, providing tools and endpoints for server-sent events and message handling.
Last updated -
131
11
MIT License
Provides a module for NestJS to create an MCP (Model Context Protocol) server with Server-Sent Events (SSE) transport, allowing services to be exposed as tools that clients can discover and execute.
Enables sending continuous progress updates from tools to clients, allowing for tracking of long-running operations with percentage completion indicators.
Integrates Zod schema validation for tool requests, enabling type-safe parameter validation for tools exposed through the MCP server.
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
🚀 Support for all Transport Types:
Streamable HTTP
HTTP+SSE
STDIO
🔍 Automatic
tool,resource, andpromptdiscovery and registration💯 Zod-based tool call validation
📊 Progress notifications
🔒 Guard-based authentication
🌐 Access to HTTP Request information within MCP Resources (Tools, Resources, Prompts)
Installation
npm install @rekog/mcp-nest @modelcontextprotocol/sdk zod
Quick Start
1. Import 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 Resource
// greeting.tool.ts
import type { Request } from 'express';
import { Injectable } from '@nestjs/common';
import { Tool, Resource, 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, request: Request) {
const userAgent = request.get('user-agent') || 'Unknown';
const greeting = `Hello, ${name}! Your user agent is: ${userAgent}`;
const totalSteps = 5;
for (let i = 0; i < totalSteps; i++) {
await new Promise((resolve) => setTimeout(resolve, 100));
// Send a progress update.
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 the parameters and URI in the same object.
async getCurrentSchema({ uri, userName }) {
return {
content: [
{
uri,
text: `User is ${userName}`,
mimeType: 'text/plain',
},
],
};
}
}
You are done!
TIP
The above example shows how HTTPRequest headers are accessed within MCP Tools. This is useful for identifying users, adding client-specific logic, and many other use cases. For more examples, see the Authentication Tests.
Quick Start for STDIO
The main difference is that you need to provide the transport option when importing the module.
McpModule.forRoot({
name: 'playground-stdio-server',
version: '0.0.1',
transport: McpTransportType.STDIO,
});
The rest is the same, you can define tools, resources, and prompts as usual. An example of a standalone NestJS application using the STDIO transport is the following:
async function bootstrap() {
const app = await NestFactory.createApplicationContext(AppModule, {
logger: false,
});
return app.close();
}
void bootstrap();
Next, you can use the MCP server with an MCP Stdio Client (see example), or after building your project you can use it with the following MCP Client configuration:
{
"mcpServers": {
"greeting": {
"command": "node",
"args": [
"<path to dist js file>",
]
}
}
}
API Endpoints
HTTP+SSE transport exposes two endpoints:
GET /sse: SSE connection endpoint (Protected by guards if configured)POST /messages: Tool execution endpoint (Protected by guards if configured)
Streamable HTTP transport exposes the following endpoints:
POST /mcp: Main endpoint for all MCP operations (tool execution, resource access, etc.). In stateful mode, this creates and maintains sessions.GET /mcp: Establishes Server-Sent Events (SSE) streams for real-time updates and progress notifications. Only available in stateful mode.DELETE /mcp: Terminates MCP sessions. Only available in stateful mode.
Tips
It's possible to use the module with global prefix, but the recommended way is to exclude those endpoints with:
app.setGlobalPrefix('/api', { exclude: ['sse', 'messages', 'mcp'] });
Authentication
You can secure your MCP endpoints using standard NestJS Guards.
1. Create a Guard
Implement the CanActivate interface. The guard should handle request validation (e.g., checking JWTs, API keys) and optionally attach user information to the request object.
Nothing special, check the NestJS documentation for more details.
2. Apply the Guard
Pass your guard(s) to the McpModule.forRoot configuration. The guard(s) will be applied to both 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], // Ensure the Guard is also provided
})
export class AppModule {}
That's it! The rest is the same as NestJS Guards.
Playground
The playground directory contains examples to quickly test MCP and @rekog/mcp-nest features.
Refer to the playground/README.md for more details.
Configuration
The McpModule.forRoot() method accepts an McpOptions object to configure the server. Here are the available options:
Option | Description | Default |
| Required. The name of your MCP server. | - |
| Required. The version of your MCP server. | - |
| Optional MCP server capabilities to advertise. See . |
|
| Optional instructions for the client on how to interact with the server. |
|
| Specifies the transport type(s) to enable. |
|
| The endpoint path for the SSE connection (used with
transport). |
|
| The endpoint path for sending messages (used with
transport). |
|
| The base endpoint path for MCP operations (used with
transport). |
|
| A global prefix for all MCP endpoints. Useful if integrating into an existing application. |
|
| An array of NestJS Guards to apply to the MCP endpoints for authentication/authorization. |
|
| An array of NestJS Class Decorators to apply to the generated MCP controllers. |
|
| Configuration specific to the
transport. |
|
| Whether to enable periodic SSE ping messages to keep the connection alive. |
|
| The interval (in milliseconds) for sending SSE ping messages. |
|
| Configuration specific to the
transport. |
|
| If
, allows the
endpoint to return JSON responses for non-streaming requests (like
). |
|
| A function to generate unique session IDs when running in stateful mode. Required if
is
. |
|
| If
, the
transport operates statelessly (no sessions). If
, it operates statefully, requiring a
. |
|
This server cannot be installed
remote-capable server
The server can be hosted and run remotely because it primarily relies on remote services or has no dependency on the local environment.
A NestJS module that allows services to be exposed as an MCP server with Server-Sent Events transport, facilitating tool discovery and execution by clients.
- Features
- Installation
- Quick Start
- Quick Start for STDIO
- API Endpoints
- Authentication
- Playground
- Configuration
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