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Function Calling empowers AI models to interact with external tools and APIs, enabling them to perform specific actions and access real-time information. This capability extends the functionality of AI models beyond simple text generation, allowing for more dynamic and practical applications.

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Supported Models

The following models support Function Calling:

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Quick Start Guide

This guide demonstrates how to use Function Calling to retrieve current weather information for a user’s specified location. We will walk through a complete Python code example. For the specific API format of Function Calling, please refer to the API reference Create Chat Completion.

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1. Initialize the Client

First, you need to initialize the client with your Novita API key. 
from openai import OpenAI
import json

client = OpenAI(
    base_url="https://api.novita.ai/openai",
    # Get the Novita AI API Key from: https://novita.ai/settings/key-management.
    api_key="<YOUR Novita AI API Key>",
)

model = "deepseek/deepseek_v3"

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2. Define the Function to Be Called

Next, define the Python function that the model can call. In this example, it’s a function to get weather information. 
# Example function to simulate fetching weather data.
def get_weather(location):
    """Retrieves the current weather for a given location."""
    print("Calling get_weather function with location: ", location)
    # In a real application, you would call an external weather API here.
    # This is a simplified example returning hardcoded data.
    return json.dumps({"location": location, "temperature": "60 degrees Fahrenheit"})

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3. Construct the API Request with Tools and User Message

Now, create the API request to the Novita endpoint. This request includes the tools parameter, defining the functions the model can use, and the user’s message. 
tools = [
    {
        "type": "function",
        "function": {
            "name": "get_weather",
            "description": "Get weather of an location, the user shoud supply a location first",
            "parameters": {
                "type": "object",
                "properties": {
                    "location": {
                        "type": "string",
                        "description": "The city and state, e.g. San Francisco, CA",
                    }
                },
                "required": ["location"]
            },
        }
    },
]

messages = [
    {
        "role": "user",
        "content": "What is the weather in San Francisco?"
    }
]

# Let's send the request and print the response.
response = client.chat.completions.create(
    model=model,
    messages=messages,
    tools=tools,
)

# Please check if the response contains tool calls if in production.
tool_call = response.choices[0].message.tool_calls[0]
print(tool_call.model_dump())
Output: 
{'id': '0', 'function': {'arguments': '{"location": "San Francisco, CA"}', 'name': 'get_weather'}, 'type': 'function'}

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4. Respond with the Function Call Result and Get the Final Answer

The next step is to process the function call, execute the get_weather function, and send the result back to the model to generate the final response to the user. 
# Ensure tool_call is defined from the previous step
if tool_call:
    # Extend conversation history with the assistant's tool call message
    messages.append(response.choices[0].message)

    function_name = tool_call.function.name
    if function_name == "get_weather":
        function_args = json.loads(tool_call.function.arguments)
        # Execute the function and get the response
        function_response = get_weather(
            location=function_args.get("location"))
        # Append the function response to the messages
        messages.append(
            {
                "tool_call_id": tool_call.id,
                "role": "tool",
                "content": function_response,
            }
        )

    # Get the final response from the model, now with the function result
    answer_response = client.chat.completions.create(
        model=model,
        messages=messages,
        # Note: Do not include tools parameter here.
    )
    print(answer_response.choices[0].message)
Output: 
ChatCompletionMessage(content="The weather in San Francisco, CA is currently **60 degrees Fahrenheit**. For more detailed information, such as specific conditions (e.g., sunny, cloudy, rainy), you might want to check a local weather app or website. Let me know if you'd like help with anything else!", refusal=None, role='assistant', function_call=None, tool_calls=None)

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The Complete Code

from openai import OpenAI
import json

client = OpenAI(
    base_url="https://api.novita.ai/openai",
    # Get the Novita AI API Key from: https://novita.ai/settings/key-management.
    api_key="<YOUR Novita AI API Key>",
)

model = "deepseek/deepseek_v3"

# Example function to simulate fetching weather data.
def get_weather(location):
    """Retrieves the current weather for a given location."""
    print("Calling get_weather function with location: ", location)
    # In a real application, you would call an external weather API here.
    # This is a simplified example returning hardcoded data.
    return json.dumps({"location": location, "temperature": "60 degrees Fahrenheit"})

tools = [
    {
        "type": "function",
        "function": {
            "name": "get_weather",
            "description": "Get weather of an location, the user shoud supply a location first",
            "parameters": {
                "type": "object",
                "properties": {
                    "location": {
                        "type": "string",
                        "description": "The city and state, e.g. San Francisco, CA",
                    }
                },
                "required": ["location"]
            },
        }
    },
]

messages = [
    {
        "role": "user",
        "content": "What is the weather in San Francisco?"
    }
]

# Let's send the request and print the response.
response = client.chat.completions.create(
    model=model,
    messages=messages,
    tools=tools,
)

# Please check if the response contains tool calls if in production.
tool_call = response.choices[0].message.tool_calls[0]
print(tool_call.model_dump())

# Ensure tool_call is defined from the previous step
if tool_call:
    # Extend conversation history with the assistant's tool call message
    messages.append(response.choices[0].message)

    function_name = tool_call.function.name
    if function_name == "get_weather":
        function_args = json.loads(tool_call.function.arguments)
        # Execute the function and get the response
        function_response = get_weather(
            location=function_args.get("location"))
        # Append the function response to the messages
        messages.append(
            {
                "tool_call_id": tool_call.id,
                "role": "tool",
                "content": function_response,
            }
        )

    # Get the final response from the model, now with the function result
    answer_response = client.chat.completions.create(
        model=model,
        messages=messages,
        # Note: Do not include tools parameter here
    )
    print(answer_response.choices[0].message)
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