Build an MCP server with Deno

An MCP server exposes tools, resources, and prompts to AI clients through a protocol. Deno is a natural fit for a local stdio server: single-file TypeScript, explicit permissions, and no separate compile step.

deno add npm:@modelcontextprotocol/sdk npm:zod

import { McpServer } from "@modelcontextprotocol/sdk/server/mcp.js";
import { StdioServerTransport } from "@modelcontextprotocol/sdk/server/stdio.js";
import { z } from "zod";

const server = new McpServer({ name: "project-info", version: "1.0.0" });

server.registerTool(
  "read_project_note",
  {
    description: "Read one approved note by its short name",
    inputSchema: { name: z.string().regex(/^[a-z0-9-]+$/) },
  },
  async ({ name }) => ({
    content: [{
      type: "text",
      text: await Deno.readTextFile(`./notes/${name}.md`),
    }],
  }),
);

await server.connect(new StdioServerTransport());

Grant the client read access only to the notes directory:

{
  "mcpServers": {
    "project-info": {
      "command": "deno",
      "args": ["run", "--allow-read=./notes", "mcp_server.ts"]
    }
  }
}

Prefer Streamable HTTP for remote servers. The old HTTP+SSE transport exists only for compatibility. A public deployment also needs authentication, Origin and DNS-rebinding defenses, rate limits, and authorization on every tool call.

Official references: Deno MCP server example, MCP TypeScript SDK server, and Model Context Protocol.