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# onFunctionCall

> Pre-execution hook called before each SWAIG function invocation.

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

Pre-execution hook called before each SWAIG function is executed. The default
implementation is a no-op. Override this method in a subclass to intercept tool
calls for logging, metrics, or custom dispatch logic.

> **Note**
>
> Return a result object from this hook to **short-circuit** default execution —
> the returned value is sent as the function response and the registered tool
> handler is skipped. Return `void` / `undefined` to let the normal dispatch
> proceed.

## **Parameters**

**`name`** `string` — required

Name of the SWAIG function about to execute.

---

**`args`** `Record<string, unknown>` — required

Parsed arguments for the function, conforming to the function's parameter schema.

---

**`rawData`** `Record<string, unknown>` — required

The full raw SWAIG request payload, including metadata such as
`call_id`, `caller_id_number`, and `global_data`.

---

## **Returns**

`Record<string, unknown> | void | Promise<Record<string, unknown> | void>` --
Return a result object to short-circuit default execution; return `void` /
`undefined` to proceed normally.

## **Example**

```typescript {25}
import { AgentBase } from '@signalwire/sdk';

class LoggingAgent extends AgentBase {
  constructor() {
    super({ name: 'logging-agent', route: '/logging' });
    this.setPromptText('You are a helpful assistant.');
    this.defineTools();
  }

  protected override defineTools(): void {
    this.defineTool({
      name: 'lookup_order',
      description: 'Look up an order',
      parameters: {
        type: 'object',
        properties: { order_id: { type: 'string' } },
        required: ['order_id'],
      },
      handler: async (args) => {
        return { response: `Order ${args.order_id} is in transit.` };
      },
    });
  }

  override async onFunctionCall(
    name: string,
    args: Record<string, unknown>,
    rawData: Record<string, unknown>,
  ): Promise<void> {
    const callId = (rawData.call_id as string) ?? 'unknown';
    console.log(`[${callId}] Tool called: ${name}(${JSON.stringify(args)})`);
  }
}

const agent = new LoggingAgent();
await agent.serve();
```

> Pre-execution hook called before each SWAIG function invocation.