In this tutorial, we’ll explore how to create and use a simple WeatherLogger agent. This agent can check the current weather and log the info to a human-readable format. You can play around with this example at Jupyter notebook.

​
WeatherLogger class

This is a straightforward implementation of the Tool class, designed to perform two primary operations: checking the weather (observation) and logging the information (action). 
import os
from dotenv import load_dotenv
import requests
from toolfuse import Tool, action, observation

class WeatherLogger(Tool):
    def __init__(self):
        super().__init__()
        self.log_file = "weather.txt"

    @action
    def log(self, message: str):
        """Logs a message to the log file."""
        with open(self.log_file, "a") as file:
            file.write("***\n" + message + "\n")

    @observation
    def weather(self, location: str) -> str:
        """Checks the current weather from the internet using wttr.in."""
        weather_api_url = f"http://wttr.in/{location}?format=%l:+%C+%t"
        try:
            response = requests.get(weather_api_url)
            return response.text
        except requests.exceptions.HTTPError as err:
            return f"HTTP Error: {err}"
        except requests.exceptions.RequestException as e:
            return f"Error: Could not retrieve weather data. {e}"

# Example usage
tool = WeatherLogger()
location = "Paris"
weather_info = tool.weather(location)
print(f"Weather in {location}: {weather_info}")
tool.log(f"Weather in {location}: {weather_info}")
Pretty trivial, as you can see.

​
Communication with LLM

The interesting part though is not really the ability to use weather API and write to files, but to use this class to give an LLM a new skill. All we have to do is get the schema of the tool actions and observations and give them to our LLM like this: 
schema = tool.json_schema()

[{'name': 'log',
  'parameters': {'type': 'object',
   'properties': {'message': {'type': 'string'}},
   'required': ['message']},
  'description': 'Logs a message to the log file.'},
 {'name': 'weather',
  'parameters': {'type': 'object',
   'properties': {'location': {'type': 'string'}},
   'required': ['location']},
  'description': 'Checks the current weather from the internet using wttr.in.'}]
As you can see, the schema object lists all actions we have with their parameters and descriptions. Now that we have this info, we can implement a simple scenario:
  • We inform the AI about the tools (in our case, weather and log) that it can use.
  • We give it a task to check and describe weather in a given city.
First things first: We start with a prompt. As you can see, it contains the schema of the tool and the instructions on how to respond. 
system_message = """You are a helpful poetical AI. 
You can check the weather, write a short poem to describe it and log all of that. 
You have the following tools available to you: 

{schema}

When you respond, always give a JSON with a correct tool called. For example:

{"tool": "weather", "parameters": {"location": "Thessaloniki"}}

{"tool": "log", "parameters": {"message": "The weather is nice."}}

Only answer with JSON. Avoid wrapping it in quotes.
"""

task = "Check the weather in Paris, describe it, and log the result."
Now, we add a couple of helper functions to make the process of interacting with the AI easier. 
# Helper functions
def ask_ai(messages):
    response = client.chat.completions.create(
        model="gpt-4-1106-preview",
        messages=messages,
        max_tokens=1000
    )
    print(f"Full response: {response}")
    assistant_reply = response.choices[0].message.content
    print(f"Actual reply: {assistant_reply}")
    return assistant_reply

def execute_step(reply, tool):
    jdict = json.loads(reply)
    print(f"Parsed JSON: {jdict}")
    action = tool.find_action(jdict['tool'])
    print(f"Found action: {action.name}")
    result = tool.use(action, **jdict['parameters'])
    print(f"Result: {result}")
    return result
The entire process after this looks as follows:
  • Update the list of messages
  • Ask the AI for the next step
  • Execute the next step
  • Repeat
  • …
  • Profit!
# Initial messages for the AI
messages = []
messages.append({"role": "system", "content": system_message})
messages.append({"role": "user", "content": task})

# First loop: Suggest checking the weather
reply = ask_ai(messages)
messages.append({"role": "assistant", "content": reply})
result = execute_step(reply, tool)
messages.append({"role": "user", "content": result})

# Second loop: Get the weather, create a poem, and log it
reply = ask_ai(messages)
messages.append({"role": "assistant", "content": reply})
result = execute_step(reply, tool)
And here we are, with a beautiful poem about the weather in Paris inside the weather.txt: 
***
Paris: Partly cloudy +11°C
***
A sky of artists' delight, in Paris so fair,
Partly clad in cloudy attire, with a cool, gentle air,
Eleven degrees holds the day in its embrace,
While sun and clouds in a dainty dance do chase.

​
What’s next?