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# on_function_call

> Override hook called when a SWAIG function is invoked during a conversation.

[functionresult]: /docs/server-sdks/reference/python/agents/function-result

[define-tool]: /docs/server-sdks/reference/python/agents/agent-base/define-tool

[tool-decorator]: /docs/server-sdks/reference/python/agents/agent-base#tool

Called when the SignalWire platform invokes a SWAIG function on this agent.
The default implementation looks up the function in the tool registry and
executes it. Override this method in a subclass to intercept tool calls
for logging, metrics, pre/post-processing, or custom dispatch logic.

> **Note**
>
> Most agents do not need to override this method. The default implementation
> handles function lookup, argument validation, and execution automatically.
> Token verification occurs upstream in the HTTP handler before this method is
> called. Override only when you need cross-cutting behavior across all tool calls.

> **Warning**
>
> This method **is** the tool dispatch mechanism. If you override it without calling
> `super().on_function_call(name, args, raw_data)`, the registered tool handler will
> **not** execute. Always call `super()` to preserve default dispatch behavior.

## **Parameters**

**`name`** `str` — required

The name of the SWAIG function being invoked.

---

**`args`** `dict[str, Any]` — required

Arguments passed by the AI, conforming to the function's parameter schema.

---

**`raw_data`** `dict[str, Any] | None` — default: None

The complete raw POST data from the SWAIG request, including metadata such as
`call_id`, `caller_id_number`, and `global_data`.

---

## **Returns**

[`FunctionResult`][functionresult] or `dict` -- The tool's response. The default
implementation returns the result of executing the registered handler.

## **Example**

```python {14-19}
from signalwire import AgentBase
from signalwire.core.function_result import FunctionResult

class LoggingAgent(AgentBase):
    def __init__(self):
        super().__init__(name="logging-agent", route="/logging")
        self.set_prompt_text("You are a helpful assistant.")

    @AgentBase.tool(description="Look up an order")
    def lookup_order(self, args, raw_data=None):
        order_id = args.get("order_id")
        return FunctionResult(f"Order {order_id} is in transit.")

    def on_function_call(self, name, args, raw_data=None):
        call_id = raw_data.get("call_id", "unknown") if raw_data else "unknown"
        print(f"[{call_id}] Tool called: {name}({args})")
        result = super().on_function_call(name, args, raw_data)
        print(f"[{call_id}] Tool result: {result}")
        return result

agent = LoggingAgent()
agent.run()
```

> Override hook called when a SWAIG function is invoked during a conversation.