Build a Public Server

Tutorial: Build a Public Server

This tutorial shows how to make a ContextVM server discoverable via CEP-6 public announcements. By announcing your server, any client on the Nostr network can find it, learn about its capabilities, and connect to it.

What you’ll build

You will create a minimal ContextVM server that:

1. Exposes an MCP tool
2. Connects to Nostr relays
3. Publishes its metadata and capabilities (CEP-6 announcements)

Prerequisites

• Node.js or Bun
• A Nostr private key (in hex format)
• Access to Nostr relays (e.g., wss://relay.contextvm.org)
• You have completed the Client-Server Communication tutorial.

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Step 1: Create a basic MCP server

First, create a basic MCP server. We will use the @modelcontextprotocol/sdk and @contextvm/sdk.

Create a file named public-server.ts:

import { McpServer } from '@modelcontextprotocol/sdk/server/mcp.js';
import {
  NostrServerTransport,
  PrivateKeySigner,
  ApplesauceRelayPool,
} from '@contextvm/sdk';
import { z } from 'zod';

// Configuration
const SERVER_PRIVATE_KEY_HEX =
  process.env.SERVER_PRIVATE_KEY || 'your-32-byte-hex-key';
const RELAYS = ['wss://relay.contextvm.org'];

async function main() {
  const signer = new PrivateKeySigner(SERVER_PRIVATE_KEY_HEX);
  const relayPool = new ApplesauceRelayPool(RELAYS);

  // Create the MCP Server
  const mcpServer = new McpServer({
    name: 'my-public-server',
    version: '1.0.0',
  });

  // Add a simple tool
  mcpServer.registerTool(
    'greet',
    {
      description: 'Greets a user by name',
      inputSchema: { name: z.string() },
    },
    async ({ name }) => ({
      content: [{ type: 'text', text: `Hello, ${name}!` }],
    }),
  );

  // Transport will be configured in Step 2...
}

main().catch(console.error);

Step 2: Enable public announcements

To make the server public, configure the NostrServerTransport with isAnnouncedServer: true.

When isAnnouncedServer is true, the transport automatically publishes NIP-01 replaceable events (kinds 11316-11320) containing the server’s metadata and its available tools, resources, and prompts.

Add the transport configuration to your script:

// ... inside main()

const serverTransport = new NostrServerTransport({
  signer,
  relayHandler: relayPool,
  isAnnouncedServer: true, // This enables CEP-6 announcements
  serverInfo: {
    name: 'Greeting Server',
    about: 'A simple server that provides greeting tools.',
    picture: 'https://example.com/avatar.png', // Optional
    website: 'https://contextvm.org', // Optional
  },
});

await mcpServer.connect(serverTransport);
console.log(`Server running. Public key: ${await signer.getPublicKey()}`);

Step 3: Run and verify

Run your server:

bun run public-server.ts

When the transport starts, it performs a simulated MCP request to itself (calling tools/list, resources/list, etc.) and publishes the results to the relays.

You can verify your server is discoverable by querying the relays for a kind: 11316 event authored by your server’s public key. You can use any Nostr client or the ContextVM discovery helpers.

# Example using nak (the standard Nostr CLI)
nak req -k 11316 -a <your-server-pubkey> wss://relay.contextvm.org

Step 4: Remove announcements

If you take your server offline permanently, you should clean up its public announcements. ContextVM uses NIP-09 deletion events (kind 5) to achieve this.

You can delete announcements using a utility script or by calling an exposed transport method (if your SDK implementation provides a cleanup function). The rs-sdk natively provides a helper for this via its announcement module.

Next Steps

• Learn how clients find your server in the Discover ContextVM Servers tutorial.
• Read the formal CEP-6 Specification.
• Use CEP-15 Common Tool Schemas to make your tools semantically interoperable.