Realtime voice agents in Swiss German

ws.send(JSON.stringify({
  type: 'session.start',
  language: 'de-CH', dialect: 'bern', voice: 'anna',
  instructions: 'Du bist die Terminvergabe der Praxis Muster. ' +
                'Sprich kurz und freundlich.',
  greeting: 'Grüezi, Praxis Muster. Wie kann ich helfen?',
  vocabulary: ['Muster', 'Dr. Brunner', 'Bremgarten'],
  input:  { encoding: 'mulaw', sample_rate_hz: 8000 },  // phone line
  output: { encoding: 'mulaw', sample_rate_hz: 8000,
            transport: 'binary' },
  turn_taking: { mode: 'auto', interruptions: true },
  tools: [{
    name: 'book_appointment',
    description: 'Books an appointment for the caller.',
    parameters: {
      type: 'object',
      properties: {
        name: { type: 'string' }, time: { type: 'string' },
      },
      required: ['name', 'time'],
    },
  }],
}));

ws.on('message', async (data, isBinary) => {
  if (isBinary) return player.write(data);     // agent's voice

  const m = JSON.parse(data.toString());
  switch (m.type) {
    case 'audio.clear':                        // caller interrupted
      player.clear(); break;
    case 'user.transcript.final':
      log('caller', m.text); break;
    case 'reply.done':
      log('agent', m.transcript); break;
    case 'tool.call': {                        // ask your backend
      const result = await bookAppointment(m.arguments);
      ws.send(JSON.stringify({
        type: 'tool.result', call_id: m.call_id,
        output: JSON.stringify(result),
      }));
      break;
    }
  }
});