LeanMCP Minimal Server

MCP Server with Streamable HTTP Transport built with LeanMCP SDK

Quick Start

# Install dependencies
npm install

# Start development server (hot reload + UI build)
npm run dev

# Build for production
npm run build

# Run production server
npm start

Project Structure

leanmcp-minimal/
├── main.ts              # Server entry point
├── mcp/                 # Services directory (auto-discovered)
│   └── example/
│       └── index.ts     # Example service
├── .env                 # Environment variables
└── package.json

Adding New Services

Create a new service directory in mcp/:

// mcp/myservice/index.ts
import { Tool, SchemaConstraint } from "@leanmcp/core";

// Define input schema
class MyToolInput {
  @SchemaConstraint({ 
    description: "Message to process",
    minLength: 1
  })
  message!: string;
}

export class MyService {
  @Tool({ 
    description: "My awesome tool",
    inputClass: MyToolInput
  })
  async myTool(input: MyToolInput) {
    return {
      content: [{
        type: "text",
        text: `You said: ${input.message}`
      }]
    };
  }
}

Services are automatically discovered and registered - no need to modify main.ts!

Adding UI Components

Use @UIApp decorator to link tools to React components:

// mcp/products/index.ts
import { Tool } from "@leanmcp/core";
import { UIApp } from "@leanmcp/ui";

export class ProductsService {
  @Tool({ description: "List products" })
  @UIApp({ component: "./ProductsDashboard" })
  async listProducts() {
    return { products: [...] };
  }
}

// mcp/products/ProductsDashboard.tsx
import { ToolDataGrid, RequireConnection } from "@leanmcp/ui";

export function ProductsDashboard() {
  return (
    <RequireConnection loading={<div>Loading...</div>}>
      <ToolDataGrid toolName="listProducts" columns={[...]} />
    </RequireConnection>
  );
}

The CLI automatically builds UI components and wraps them with AppProvider.

Features

• Zero-config auto-discovery - Services automatically registered from ./mcp directory
• Type-safe decorators - @Tool, @Prompt, @Resource with full TypeScript support
• Schema validation - Automatic input validation with @SchemaConstraint
• HTTP transport - Production-ready HTTP server with session management
• Hot reload - Development mode with automatic restart on file changes
• UI Components - React UI components with @UIApp decorator

Testing with MCP Inspector

npx @modelcontextprotocol/inspector http://localhost:3001/mcp

License

MIT