JavaScript tool-calling agent

import OpenAI from "openai";

const client = new OpenAI({
  apiKey: process.env.ORQEN_API_KEY,
  baseURL: "https://api.orqen.app/v1",
});

const tools = [
  {
    type: "function",
    function: {
      name: "get_weather",
      description: "Get current weather for a city.",
      parameters: {
        type: "object",
        properties: { city: { type: "string" } },
        required: ["city"],
      },
    },
  },
];

async function callTool(name, args) {
  if (name === "get_weather") {
    return { city: args.city, temperature_c: 13, conditions: "light rain" };
  }
  return { error: "Unknown tool" };
}

async function run(userMessage) {
  const messages = [{ role: "user", content: userMessage }];
  for (let i = 0; i < 8; i++) {
    const response = await client.chat.completions.create({
      model: "gpt-4o",
      messages,
      tools,
      tool_choice: "auto",
    });
    const message = response.choices[0].message;
    if (!message.tool_calls?.length) return message.content ?? "";
    messages.push(message);
    for (const call of message.tool_calls) {
      const args = JSON.parse(call.function.arguments || "{}");
      const result = await callTool(call.function.name, args);
      messages.push({
        role: "tool",
        tool_call_id: call.id,
        content: JSON.stringify(result),
      });
    }
  }
  return "Stopped after max tool rounds.";
}

console.log(await run("What is the weather in London?"));

const stream = await client.chat.completions.create({
  model: "gpt-4o",
  messages: [{ role: "user", content: "Explain agent payload optimization" }],
  tools,
  stream: true,
});

for await (const chunk of stream) {
  process.stdout.write(chunk.choices[0]?.delta?.content ?? "");
}