Does Gemini have a system prompt option while making an API request?

[Talcum9808]

I am making an app and OpenAI's ChatGPT and Anthropic's Claude has a System Prompt option to provide context, instructions, and guidelines before presenting it with a question or task. Even Cohere's Coral has an equivalent Preamble Override for this. I tried the below method but it gives me inconsistent results. Is there any other way efficient way to achieve this? Does Gemini have a system prompt equivalent option?

const chat = model.startChat({
                    history: [
                        {
                            role: "user",
                            parts: "Hi."

                        },
                        {
                            role: "model",
                            parts: "I will only respond in Spanish"
                        }
                    ],
                });