AI Agents - lesson 3 | HackIndia Skills

AI Agents - lesson 3 | HackIndia Skills | HackIndia

Example

Minimal loop

This is the shape you want in your repo. The callModel function stands for whichever model API or SDK you use. Keep the loop code separate from the tool functions.

This example uses one fake campus tool so you can test the flow without paid APIs.

const tools = {
  get_canteen_menu: async ({ day }) => {
    const menus = {
      monday: 'Idli, sambar, chai',
      tuesday: 'Poha, bread omelette, chai',
      wednesday: 'Paratha, curd, chai'
    };

    return menus[day.toLowerCase()] || 'Menu not available';
  }
};

async function runAgent(userMessage) {
  const messages = [{ role: 'user', content: userMessage }];

  while (true) {
    const response = await callModel({
      messages,
      tools: [
        {
          name: 'get_canteen_menu',
          description: 'Get the college canteen breakfast menu for a day',
          parameters: {
            type: 'object',
            properties: {
              day: { type: 'string', description: 'Day name, like Monday' }
            },
            required: ['day']
          }
        }
      ]
    });

    messages.push(response.message);

    if (!response.toolCalls || response.toolCalls.length === 0) {
      return response.message.content;
    }

    for (const call of response.toolCalls) {
      const tool = tools[call.name];
      if (!tool) throw new Error(`Unknown tool: ${call.name}`);

      const result = await tool(call.arguments);

      messages.push({
        role: 'tool',
        toolCallId: call.id,
        name: call.name,
        content: JSON.stringify(result)
      });
    }
  }
}

Tip

Log every turn

Print the model message, tool call name, arguments, and tool result while developing. It makes bugs obvious.

If the agent gives a strange final answer, your logs show whether the schema was unclear, the arguments were wrong, or the tool returned poor data.

console.log('MODEL:', response.message);
console.log('TOOL CALLS:', response.toolCalls);
console.log('TOOL RESULT:', result);

Build the call-result loop

The core loop

Who does what

Loop shape

Minimal loop

Common wrong version

Log every turn

Do this now

Quick check