Function calling with the Gemini API

Function calling lets you connect models to external tools and APIs. Instead of generating text responses, the model determines when to call specific functions and provides the necessary parameters to execute real-world actions. This allows the model to act as a bridge between natural language and real-world actions and data. Function calling has 3 primary use cases:

  • Take Actions: Interact with external systems using APIs, such as scheduling appointments, creating invoices, sending emails, or controlling smart home devices.
  • Augment Knowledge: Access information from external sources like databases, APIs, and knowledge bases.
  • Extend Capabilities: Use external tools to perform computations and extend the limitations of the model, such as using a calculator or creating charts.

You can browse examples of these use cases below:

Schedule Meeting

This example shows how to define a function that schedules a meeting with attendees at a specific time, allowing the model to parse user requests and return structured arguments to trigger actions in external systems.

Python

from google import genai

schedule_meeting_function = {
    "type": "function",
    "name": "schedule_meeting",
    "description": "Schedules a meeting with specified attendees at a given time and date.",
    "parameters": {
        "type": "object",
        "properties": {
            "attendees": {"type": "array", "items": {"type": "string"}},
            "date": {"type": "string", "description": "Date (e.g., '2024-07-29')"},
            "time": {"type": "string", "description": "Time (e.g., '15:00')"},
            "topic": {"type": "string", "description": "The meeting topic."},
        },
        "required": ["attendees", "date", "time", "topic"],
    },
}

client = genai.Client()

interaction = client.interactions.create(
    model="gemini-3.7-flash",
    input="Schedule a meeting with Bob and Alice for 03/14/2025 at 10:00 AM about Q3 planning.",
    tools=[{"type": "function", **schedule_meeting_function}],
)

for step in interaction.steps:
    if step.type == "function_call":
        print(f"Function to call: {step.name}")
        print(f"Arguments: {step.arguments}")

JavaScript

import { GoogleGenAI } from '@google/genai';

const client = new GoogleGenAI({});

const scheduleMeetingFunction = {
  type: 'function',
  name: 'schedule_meeting',
  description: 'Schedules a meeting with specified attendees at a given time and date.',
  parameters: {
    type: 'object',
    properties: {
      attendees: { type: 'array', items: { type: 'string' } },
      date: { type: 'string', description: 'Date (e.g., "2024-07-29")' },
      time: { type: 'string', description: 'Time (e.g., "15:00")' },
      topic: { type: 'string', description: 'The meeting topic.' },
    },
    required: ['attendees'