Set system instructions to Gemini 1.5 Pro

This sample shows you how to set system instructions to Gemini 1.5 Pro.

Code sample

C#

Before trying this sample, follow the C# setup instructions in the Vertex AI quickstart using client libraries. For more information, see the Vertex AI C# API reference documentation.

To authenticate to Vertex AI, set up Application Default Credentials. For more information, see Set up authentication for a local development environment. 


using Google.Cloud.AIPlatform.V1;
using System;
using System.Threading.Tasks;

public class SystemInstruction
{
    public async Task<string> SetSystemInstruction(
        string projectId = "your-project-id",
        string location = "us-central1",
        string publisher = "google",
        string model = "gemini-2.0-flash-001")
    {

        var predictionServiceClient = new PredictionServiceClientBuilder
        {
            Endpoint = $"{location}-aiplatform.googleapis.com"
        }.Build();

        string prompt = @"User input: I like bagels.
Answer:";

        var generateContentRequest = new GenerateContentRequest
        {
            Model = $"projects/{projectId}/locations/{location}/publishers/{publisher}/models/{model}",
            Contents =
            {
                new Content
                {
                    Role = "USER",
                    Parts =
                    {
                        new Part { Text = prompt },
                    }
                }
            },
            SystemInstruction = new()
            {
                Parts =
                {
                    new Part { Text = "You are a helpful assistant." },
                    new Part { Text = "Your mission is to translate text in English to French." },
                }
            }
        };

        GenerateContentResponse response = await predictionServiceClient.GenerateContentAsync(generateContentRequest);

        string responseText = response.Candidates[0].Content.Parts[0].Text;
        Console.WriteLine(responseText);

        return responseText;
    }
}

Node.js

Before trying this sample, follow the Node.js setup instructions in the Vertex AI quickstart using client libraries. For more information, see the Vertex AI Node.js API reference documentation.

To authenticate to Vertex AI, set up Application Default Credentials. For more information, see Set up authentication for a local development environment. 

const {VertexAI} = require('@google-cloud/vertexai');

/**
 * TODO(developer): Update these variables before running the sample.
 */
async function set_system_instruction(projectId = 'PROJECT_ID') {
  const vertexAI = new VertexAI({project: projectId, location: 'us-central1'});

  const generativeModel = vertexAI.getGenerativeModel({
    model: 'gemini-2.0-flash-001',
    systemInstruction: {
      parts: [
        {text: 'You are a helpful language translator.'},
        {text: 'Your mission is to translate text in English to French.'},
      ],
    },
  });

  const textPart = {
    text: `
    User input: I like bagels.
    Answer:`,
  };

  const request = {
    contents: [{role: 'user', parts: [textPart]}],
  };

  const resp = await generativeModel.generateContent(request);
  const contentResponse = await resp.response;
  console.log(JSON.stringify(contentResponse));
}

What's next

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