Function Tools

Turn any Python function into a tool with one decorator.

Function Tools allow your agent to execute your own Python functions.

Instead of only generating text, your agent can call Python code to perform actions.

Create a Function Tool#

Python

from abzagent import function_tool

@function_tool
def get_weather(city: str):
    return f"The weather in {city} is sunny."

Register a Tool#

Python

agent = Agent(
    name="Weather Assistant",
    instructions="Help users with weather information.",
    model="gemini-2.5-flash",
    tools=[get_weather]
)

Examples#

Python

result = agent.run("What's the weather in Karachi?")

print(result.content)

How It Works#

The @function_tool decorator inspects your function's signature and turns it into a tool the model can call.
During run(), the model decides on its own whether calling the tool would help answer the prompt.
If it does, the SDK executes your Python function with the arguments the model chose and feeds the result back to the model.
The model then uses that result to generate its final response.

What Can You Build?#

Weather APIs
Calculators
Database Queries
File Management
Email Automation
Web Search
External APIs
Custom Business Logic

Best Practices#

Keep each tool focused on one task.
Give tools descriptive names.
Return predictable results.
Keep tool logic reusable.

Next Step#

Continue to Built-in Tools.