Implementing OpenAI Function Calling in Node.js

Function calling lets LLMs interact with your APIs. Here’s a production pattern:

const tools = [{
  type: 'function',
  function: {
    name: 'get_weather',
    description: 'Get current weather for a location',
    parameters: {
      type: 'object',
      properties: {
        location: { type: 'string', description: 'City name' },
        unit: { type: 'string', enum: ['celsius', 'fahrenheit'] }
      },
      required: ['location']
    }
  }
}];

const functions = {
  get_weather: async ({ location, unit = 'celsius' }) => {
    // Your API call here
    return { temp: 22, condition: 'sunny', location };
  }
};

async function chat(message) {
  const response = await openai.chat.completions.create({
    model: 'gpt-4',
    messages: [{ role: 'user', content: message }],
    tools
  });

  const toolCalls = response.choices[0].message.tool_calls;
  if (toolCalls) {
    for (const call of toolCalls) {
      const fn = functions[call.function.name];
      const args = JSON.parse(call.function.arguments);
      const result = await fn(args);
      console.log(result);
    }
  }
}