onFunctionCall | SignalWire

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.

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

stringRequired

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

1 import { AgentBase } from '@signalwire/sdk';
2 
3 class LoggingAgent extends AgentBase {
4   constructor() {
5     super({ name: 'logging-agent', route: '/logging' });
6     this.setPromptText('You are a helpful assistant.');
7     this.defineTools();
8   }
9 
10   protected override defineTools(): void {
11     this.defineTool({
12       name: 'lookup_order',
13       description: 'Look up an order',
14       parameters: {
15         type: 'object',
16         properties: { order_id: { type: 'string' } },
17         required: ['order_id'],
18       },
19       handler: async (args) => {
20         return { response: `Order ${args.order_id} is in transit.` };
21       },
22     });
23   }
24 
25   override async onFunctionCall(
26     name: string,
27     args: Record<string, unknown>,
28     rawData: Record<string, unknown>,
29   ): Promise<void> {
30     const callId = (rawData.call_id as string) ?? 'unknown';
31     console.log(`[${callId}] Tool called: ${name}(${JSON.stringify(args)})`);
32   }
33 }
34 
35 const agent = new LoggingAgent();
36 await agent.serve();