Custom Tool Events

Yield a custom CustomEvent subclass from an async @tool and consume it while streaming agent.arun().

Yield custom events from a custom tool and consume them while streaming.

This example omits stream_events=True, so Agno discards the yielded custom event. Add the option before running.

custom_tool_events.py

"""This example demonstrate how to yield custom events from a custom tool."""

import asyncio
from dataclasses import dataclass
from typing import Optional

from agno.agent import Agent
from agno.models.openai import OpenAIChat
from agno.run.agent import CustomEvent
from agno.tools import tool

# ---------------------------------------------------------------------------
# Create Agent
# ---------------------------------------------------------------------------


# Our custom event, extending the CustomEvent class
@dataclass
class CustomerProfileEvent(CustomEvent):
    """CustomEvent for customer profile."""

    customer_name: Optional[str] = None
    customer_email: Optional[str] = None
    customer_phone: Optional[str] = None


# Our custom tool
@tool()
async def get_customer_profile():
    """Example custom tool that simply yields a custom event."""

    yield CustomerProfileEvent(
        customer_name="John Doe",
        customer_email="[e-mail]",
        customer_phone="1234567890",
    )


# Setup an Agent with our custom tool.
agent = Agent(
    model=OpenAIChat(id="gpt-5.6-luna"),
    tools=[get_customer_profile],
    instructions="Your task is to retrieve customer profiles for the user.",
)


async def run_agent():
    # Running the Agent: it should call our custom tool and yield the custom event
    async for event in agent.arun(
        "Hello, can you get me the customer profile for customer with ID 123?",
        stream=True,
    ):
        if isinstance(event, CustomEvent):
            print(f"Custom event emitted: {event}")


# ---------------------------------------------------------------------------
# Run Agent
# ---------------------------------------------------------------------------
if __name__ == "__main__":
    asyncio.run(run_agent())

Run the Example

1. Set up your virtual environment

   Mac

   uv venv --python 3.12
   source .venv/bin/activate
   
2. Install dependencies

   uv pip install -U agno openai
   
3. Export your OpenAI API key

   Mac/Linux

   export OPENAI_API_KEY="your_openai_api_key_here"
   
4. Enable custom events

   In the saved file, add stream_events=True next to stream=True in the agent.arun() call.

5. Run the example

   Save the code above as custom_tool_events.py, then run:

   python custom_tool_events.py
   

Full source: cookbook/91_tools/custom_tool_events.py