MCP server and client code. Client code requires `OPENAI_API_KEY` as an environment variable. Server can be deployed as a single file to Deno Deploy: https://dash.deno.com/playground/dmcp-server

client.ts

import OpenAI from "jsr:@openai/[email protected]";
const client = new OpenAI();

const res = await client.responses.create({
  model: "o4-mini",
  input: "Roll 10d6 + 1",
  tools: [{
    type: "mcp",
    server_label: "dmcp",
    server_url: "https://dmcp-server.deno.dev/sse",
    server_description: "DMCP - MCP for Dungeons and Dragons",
    allowed_tools: ["roll"],
    require_approval: "never",
  }],
});

console.log(JSON.stringify(res.output, null, 2));
console.log("\n" + res.output_text);

server.ts

import { FastMCP } from "npm:[email protected]";
import { z } from "npm:[email protected]";
import { roll } from "npm:@half-elf/[email protected]";

const server = new FastMCP({
  name: "DMCP - MCP for Dungeons and Dragons",
  version: "0.1.0",
});

const description = `
  Given a string of text describing a dice roll in Dungeons and Dragons,
  provide a random result of the roll.

  Example input: 2d6 + 1d4
  Example output: 14
`;

server.addTool({
  name: "roll",
  description,
  parameters: z.object({ diceRollExpression: z.string() }),
  execute: async (args) => {
    return String(roll(args.diceRollExpression));
  },
});

server.start({
  transportType: "httpStream",
  httpStream: { port: parseInt(Deno.env.get("PORT") || "8000") },
});