POST /api/v2/conversations/calls returning 400 in Electron renderer

Stuck on routing outbound WebRTC sessions through POST /api/v2/conversations/calls within my Electron renderer process. While fetch dispatches to: { phoneNumber: '15551234567' } alongside from: { id: agentId }, the gateway rejects it with HTTP 400 and a validationError demanding routingData.queueId. Bearer tokens check out via ipcMain.handle('getAuthToken').

How should I structure the routingData object when the softphone already maintains an established WebSocket connection for media negotiation?