curl --request POST \
  --url https://api.highwayapi.ai/v3/gemini-2.5-flash-tts \
  --header 'Authorization: <authorization>' \
  --header 'Content-Type: <content-type>' \
  --data '
{
  "contents": {
    "role": "<string>",
    "parts": {
      "text": "<string>"
    }
  },
  "generation_config": {
    "temperature": 123,
    "speech_config": {
      "voice_config": {
        "prebuilt_voice_config": {
          "voice_name": "<string>"
        }
      },
      "language_code": "<string>",
      "multi_speaker_voice_config": {
        "speaker_voice_configs": [
          {
            "speaker": "<string>",
            "voice_config": {
              "prebuilt_voice_config": {
                "voice_name": "<string>"
              }
            }
          }
        ]
      }
    }
  }
}
'

{
  "audioContent": "<string>",
  "usageMetadata": {
    "totalTokenCount": 123,
    "promptTokenCount": 123,
    "candidatesTokenCount": 123
  }
}