Simple MCP Server Tutorial

#!/usr/bin/env node import { Server } from "@modelcontextprotocol/sdk/server/index.js"; import { StdioServerTransport } from "@modelcontextprotocol/sdk/server/stdio.js"; import { CallToolRequestSchema, ListToolsRequestSchema, } from "@modelcontextprotocol/sdk/types.js"; const server = new Server( { name: "simple-mcp-server", version: "1.0.0", }, { capabilities: { tools: {}, }, } ); // In-memory storage for notes const notes = new Map(); // List available tools server.setRequestHandler(ListToolsRequestSchema, async () => { return { tools: [ { name: "calculator", description: "Perform basic arithmetic operations (add, subtract, multiply, divide)", inputSchema: { type: "object", properties: { operation: { type: "string", enum: ["add", "subtract", "multiply", "divide"], description: "The arithmetic operation to perform", }, a: { type: "number", description: "First number", }, b: { type: "number", description: "Second number", }, }, required: ["operation", "a", "b"], }, }, { name: "add_note", description: "Add a note with a title and content", inputSchema: { type: "object", properties: { title: { type: "string", description: "The title of the note", }, content: { type: "string", description: "The content of the note", }, }, required: ["title", "content"], }, }, { name: "get_note", description: "Retrieve a note by its title", inputSchema: { type: "object", properties: { title: { type: "string", description: "The title of the note to retrieve", }, }, required: ["title"], }, }, { name: "list_notes", description: "List all note titles", inputSchema: { type: "object", properties: {}, }, }, { name: "delete_note", description: "Delete a note by its title", inputSchema: { type: "object", properties: { title: { type: "string", description: "The title of the note to delete", }, }, required: ["title"], }, }, ], }; }); // Handle tool calls server.setRequestHandler(CallToolRequestSchema, async (request) => { const { name, arguments: args } = request.params; try { switch (name) { case "calculator": { const { operation, a, b } = args; let result; switch (operation) { case "add": result = a + b; break; case "subtract": result = a - b; break; case "multiply": result = a * b; break; case "divide": if (b === 0) { throw new Error("Cannot divide by zero"); } result = a / b; break; default: throw new Error(`Unknown operation: ${operation}`); } return { content: [ { type: "text", text: `${a} ${operation} ${b} = ${result}`, }, ], }; } case "add_note": { const { title, content } = args; notes.set(title, { content, created: new Date().toISOString(), updated: new Date().toISOString(), }); return { content: [ { type: "text", text: `Note "${title}" has been added successfully.`, }, ], }; } case "get_note": { const { title } = args; const note = notes.get(title); if (!note) { return { content: [ { type: "text", text: `Note "${title}" not found.`, }, ], }; } return { content: [ { type: "text", text: `Title: ${title}\nContent: ${note.content}\nCreated: ${note.created}\nUpdated: ${note.updated}`, }, ], }; } case "list_notes": { const titles = Array.from(notes.keys()); if (titles.length === 0) { return { content: [ { type: "text", text: "No notes found.", }, ], }; } return { content: [ { type: "text", text: `Available notes:\n${titles.map(title => `- ${title}`).join('\n')}`, }, ], }; } case "delete_note": { const { title } = args; if (!notes.has(title)) { return { content: [ { type: "text", text: `Note "${title}" not found.`, }, ], }; } notes.delete(title); return { content: [ { type: "text", text: `Note "${title}" has been deleted successfully.`, }, ], }; } default: throw new Error(`Unknown tool: ${name}`); } } catch (error) { return { content: [ { type: "text", text: `Error: ${error.message}`, }, ], isError: true, }; } }); // Start the server async function main() { const transport = new StdioServerTransport(); await server.connect(transport); console.error("Simple MCP Server running on stdio"); } main().catch((error) => { console.error("Server error:", error); process.exit(1); });