Zero Mcp

# Zero MCP > Zero-boilerplate HTTP MCP server toolkit. Skip the weight of `@modelcontextprotocol/sdk` and start shipping MCP tools in minutes. ## Why Zero MCP instead of the official SDK? The official `@modelcontextprotocol/sdk` ships with **significant overhead**—both in dependencies and performance—while implementing features most developers never use and missing critical conveniences. Zero MCP takes the opposite approach: minimal dependencies, faster cold starts, and ergonomics that get you shipping in minutes. **What's wrong with the official SDK?** - **Dependency bloat** – Bundles 12+ packages (Express, CORS middleware, rate limiting, EventSource polyfills, PKCE utilities) even for simple tool servers - **Performance overhead** – Express-based transport stack adds latency and memory footprint versus native `node:http` - **Boilerplate hell** – Requires manual Express app setup, transport wiring, session management, and schema registration for every server - **Missing conveniences** – No Zod integration, no built-in lifecycle hooks, no automatic JSON Schema generation - **Feature bloat** – Ships stdio transports, SSE streaming, client implementations, and auth flows that 80% of tool servers never touch **What Zero MCP delivers instead:** - **2 dependencies total** – Just `zod` and `zod-to-json-schema`; nothing else pollutes your `node_modules` - **Native performance** – Built-in `node:http` server with zero middleware overhead; ideal for serverless and edge runtimes - **Instant start** – Instantiate `McpServer`, register tools, call `start()`—no Express config or transport plumbing - **Zod-first schemas** – Define tool inputs with Zod; JSON Schema generation happens automatically - **Built-in observability** – Lifecycle hooks for connections, tool calls, and errors work out of the box - **Production-ready CORS** – Spec-aligned origin validation included for browser MCP clients - **Focused scope** – Does one thing well: MCP tools over HTTP Choose the official SDK if you need the full MCP spec (stdio transports, prompts API, auth flows). Choose Zero MCP when you want a fast, lean tool server without the baggage. ## Installation ```bash npm install zero-mcp zod ``` `zero-mcp` re-exports `z`, but keeping an explicit `zod` dependency avoids bundler surprises. ## Minimal server example ```typescript import { McpServer, type ToolDefinition, z } from 'zero-mcp'; const server = new McpServer({ name: 'calculator', version: '1.0.0', }); server.tool({ name: 'add', description: 'Simple addition tool.', schema: z.object({ a: z.number().describe('First addend'), b: z.number().describe('Second addend'), }), handler: async ({ a, b }) => { return [ { type: 'text', text: `The sum of ${a} and ${b} is ${a + b}.`, }, ]; }, }); await server.start({ host: '127.0.0.1', port: 3000, path: '/mcp', }); console.log('Ready on http://127.0.0.1:3000/mcp'); // Later: await server.stop(); ``` The server spins up a native HTTP listener and responds to MCP JSON-RPC calls at `/mcp`. ## CORS controls Zero MCP validates the `Origin` header and emits CORS headers recommended by the MCP HTTP transport guidance. By default, `allowedOrigins` is set to `'*'`, which is convenient for local tooling. For production, pass an explicit allow-list: ```typescript await server.start({ allowedOrigins: ['https://my-mcp-console.example'], }); ``` ## Hooks for diagnostics and analytics Instrument behaviour by providing hooks either at construction time or when starting the server: ```typescript const server = new McpServer({ name: 'instrumented', version: '1.2.0', hooks: { onClientConnected(name, version, protocolVersion) { console.log(`[connect] ${name}@${version} via ${protocolVersion}`); }, onToolRegistered(toolName) { console.log(`[register] ${toolName}`); }, onToolCallStarted(toolName, input) { console.log(`[call:start] ${toolName}`, input); }, onToolCallFinished(toolName, input, result, elapsedMs) { console.log(`[call:finish] ${toolName} in ${elapsedMs.toFixed(1)}ms`); }, onToolCallError(toolName, input, error) { console.error(`[call:error] ${toolName}`, error); }, onToolsListRequested() { console.log('[tools] list requested'); }, onServerError(error) { console.error('[server:error]', error); }, }, }); ``` ## Example project A runnable weather server lives in [`example/`](https://github.com/SNIKO/zero-mcp/tree/main/example). Run it locally with: ```bash npm run example ``` This builds the library, compiles the example, and starts listening on `http://localhost:3005/mcp`. ## License MIT © Sergii Vashchyshchuk