> ## Documentation Index
> Fetch the complete documentation index at: https://docs.definable.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# Agent with Tools

> Build an agent that uses custom tools to take actions.

Create an agent with multiple tools. The agent decides which tools to call based on the user's message.

<Steps>
  <Step title="Create the agent">
    ```python agent_tools.py theme={null}
    from definable.agent import Agent
    from definable.tool.decorator import tool

    @tool
    def search_web(query: str) -> str:
        """Search the web for information."""
        return f"Top result for '{query}': Example search result."

    @tool
    def get_weather(city: str) -> str:
        """Get the current weather for a city."""
        return f"The weather in {city} is sunny, 72F."

    @tool
    def calculate(expression: str) -> str:
        """Evaluate a math expression."""
        return str(eval(expression))

    agent = Agent(
        model="gpt-4o",
        tools=[search_web, get_weather, calculate],
        instructions="You are a helpful assistant. Use tools when needed.",
    )

    output = agent.run("What's 42 * 17, and what's the weather in Paris?")
    print(output.content)
    ```
  </Step>

  <Step title="Install dependencies">
    <Snippet file="install-definable.mdx" />
  </Step>

  <Step title="Export your API key">
    <Snippet file="export-openai-key.mdx" />
  </Step>

  <Step title="Run">
    ```bash theme={null}
    python agent_tools.py
    ```

    The agent will call `calculate` and `get_weather` in parallel, then combine the results into a single response.
  </Step>
</Steps>