A minimal MCP (Model Context Protocol) server that provides dice rolling and coin flipping tools. Great as a starting point for building your own MCP servers.

This MCP server works with any MCP-compatible client:

• OpenAI Responses API - Add as an MCP tool
• Claude Desktop - Add to your MCP config
• MCP Chat - Add via the settings UI

const response = await openai.responses.create({
  model: "gpt-4o-mini",
  input: "Roll 3 dice for me",
  tools: [{
    type: "mcp",
    server_label: "dice",
    server_url: "https://your-val-url.web.val.run",
    require_approval: "never",
  }],
});

This val demonstrates the minimal structure for an HTTP MCP server:

1. Handle CORS - Required for browser-based clients
2. Implement initialize - Return server info and capabilities
3. Implement tools/list - Return available tools with JSON schemas
4. Implement tools/call - Execute tools and return results
5. Handle notifications - Return 204 for notifications/initialized

MCP uses JSON-RPC 2.0 over HTTP POST:

// Request
{ "jsonrpc": "2.0", "id": 1, "method": "tools/list", "params": {} }

// Response
{ "jsonrpc": "2.0", "id": 1, "result": { "tools": [...] } }

Tools return content as an array of typed blocks:

return jsonRpc(id, {
  content: [{ type: "text", text: "You rolled a 6!" }]
});

Fork this val to create your own MCP server with custom tools!