> ## Documentation Index
> Fetch the complete documentation index at: https://agno-v2.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# Add Tool After Initialization

> Attach a new tool to an existing agent at runtime with add_tool().

```python add_tool_after_initialization.py theme={null}
"""
Add Tool After Initialization
=============================

Demonstrates add tool after initialization.
"""

import random

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

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


@tool(stop_after_tool_call=True)
def get_weather(city: str) -> str:
    """Get the weather for a city."""
    # In a real implementation, this would call a weather API
    weather_conditions = ["sunny", "cloudy", "rainy", "snowy", "windy"]
    random_weather = random.choice(weather_conditions)

    return f"The weather in {city} is {random_weather}."


agent = Agent(
    model=OpenAIChat(id="gpt-5.2"),
    markdown=True,
)

# ---------------------------------------------------------------------------
# Run Agent
# ---------------------------------------------------------------------------
if __name__ == "__main__":
    agent.print_response("What can you do?", stream=True)

    agent.add_tool(get_weather)

    agent.print_response("What is the weather in San Francisco?", stream=True)
```

## Run the Example

<Snippet file="create-venv-step.mdx" />

**1. Install dependencies**

```bash theme={null}
uv pip install -U agno openai
```

**2. Export your OpenAI API key**

```bash Mac/Linux theme={null}
export OPENAI_API_KEY="your_openai_api_key_here"
```

```bash Windows theme={null}
$Env:OPENAI_API_KEY="your_openai_api_key_here"
```

**3. Run the example**

Save the code above as `add_tool_after_initialization.py`, then run:

```bash theme={null}
python add_tool_after_initialization.py
```

Full source: [cookbook/91\_tools/other/add\_tool\_after\_initialization.py](https://github.com/agno-agi/agno/blob/v3.0.4/cookbook/91_tools/other/add_tool_after_initialization.py)


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