MCP Server for Bun and Elysia

MCP Server for Bun and Elysia

An implementation of the Model Context Protocol (MCP) server using Bun and the Elysia web framework. This project enables you to create high-performance MCP servers that expose resources, tools, and prompts to LLMs through a standardized interface.

Features

• Server-Sent Events (SSE) transport implementation for Bun and Elysia
• Complete MCP protocol support with resources, tools, and prompts
• High-performance thanks to Bun's JavaScript runtime
• TypeScript support with proper type definitions
• Easy-to-use API for creating MCP-compatible servers

Prerequisites

• Bun installed on your system
• Basic familiarity with TypeScript and Elysia

Installation

# Clone the repository
git clone <your-repo-url>
cd mcp-server

# Install dependencies
bun install

Usage

Starting the server

# Start the server
bun start

# Start with hot reloading for development
bun dev

Building for production

# Build for production
bun run build

This will create a minified Node.js-compatible build in the dist directory.

Development

Project Structure

• src/index.ts - Main entry point for the server
• src/SSEElysiaTransport.ts - SSE transport implementation for Bun and Elysia

Creating an MCP Server

import { McpServer, ResourceTemplate } from "@modelcontextprotocol/sdk/server/mcp.js";
import { z } from "zod";
import { SSEElysiaTransport } from "./SSEElysiaTransport";
import { Elysia } from "elysia";

// Create MCP server
const server = new McpServer({
  name: "my-mcp-server",
  version: "1.0.0"
});

// Add resources, tools, and prompts
server.resource(
  "example",
  "example://resource",
  async (uri) => ({
    contents: [{
      uri: uri.href,
      text: "Example resource content"
    }]
  })
);

// Create Elysia app
const app = new Elysia()
  .get("/", () => "MCP Server")
  .get("/sse", async (context) => {
    try {
      // Create transport
      const transport = new SSEElysiaTransport("/messages", context);
      
      // Store transport
      const sessionId = transport.sessionId;
      // ... store transport in a map
      
      // Connect to MCP server
      await server.connect(transport);
      
      return;
    } catch (error) {
      // Handle error
    }
  })
  .post("/messages", async (context) => {
    // Handle incoming messages
  });

// Start server
app.listen(3001, () => {
  console.log("MCP Server running at http://localhost:3001");
});

Debugging

You can debug your MCP server using the MCP Inspector tool and connect through sse

npx @modelcontextprotocol/inspector

This will open a web interface where you can:

• List available resources, tools, and prompts
• Test calling tools and retrieving resources
• Inspect the communication between the client and server

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

License

This project is licensed under the MIT License - see the LICENSE file for details.