Use system instructions

System instructions are like a preamble that you add before the LLM gets exposed to any further instructions from the user. It lets users steer the behavior of the model based on their specific needs and use cases. When you set a system instruction, you give the model additional context to understand the task, provide more customized responses, and adhere to specific guidelines over the full user interaction with the model. For developers, product-level behavior can be specified in system instructions, separate from prompts provided by end users. For example, you can include things like the role or persona, contextual information, and formatting instructions:

You are a friendly and helpful assistant.
Ensure your answers are complete, unless the user requests a more concise approach.
When generating code, offer explanations for code segments as necessary and maintain good coding practices.
When presented with inquiries seeking information, provide answers that reflect a deep understanding of the field, guaranteeing their correctness.
For any non-english queries, respond in the same language as the prompt unless otherwise specified by the user.
For prompts involving reasoning, provide a clear explanation of each step in the reasoning process before presenting the final answer.

The following Gemini models support system instructions:

  • gemini-1.5-flash-001
  • gemini-1.5-pro-001
  • gemini-1.0-pro-002

If you're using a different model, see Assign a role instead.

You can use system instructions in many ways, including:

  • Defining a persona or role (for a chatbot, for example)
  • Defining output format (Markdown, YAML, etc.)
  • Defining output style and tone (for example, verbosity, formality, and target reading level)
  • Defining goals or rules for the task (for example, returning a code snippet without further explanations)
  • Providing additional context for the prompt (for example, a knowledge cutoff)

When a system instruction is set, it applies to the entire request. It works across multiple user and model turns when included in the prompt. Though system instructions are separate from the contents of prompt, they are still your part of your overall prompts and therefore are subject to standard data use policies.

Code samples

The code samples on the following tabs demonstrate how to use system instructions in your generative AI application.

Python

Before trying this sample, follow the Python setup instructions in the Vertex AI quickstart using client libraries. For more information, see the Vertex AI Python 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.

import vertexai

from vertexai.generative_models import GenerativeModel

# TODO(developer): Update and un-comment below lines
# project_id = "PROJECT_ID"

vertexai.init(project=project_id, location="us-central1")

model = GenerativeModel(
    model_name="gemini-1.5-flash-001",
    system_instruction=[
        "You are a helpful language translator.",
        "Your mission is to translate text in English to French.",
    ],
)

prompt = """
User input: I like bagels.
Answer:
"""

contents = [prompt]

response = model.generate_content(contents)
print(response.text)

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-1.5-pro-preview-0409',
    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));
}

Java

Before trying this sample, follow the Java setup instructions in the Vertex AI quickstart using client libraries. For more information, see the Vertex AI Java 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.

import com.google.cloud.vertexai.VertexAI;
import com.google.cloud.vertexai.api.GenerateContentResponse;
import com.google.cloud.vertexai.generativeai.ContentMaker;
import com.google.cloud.vertexai.generativeai.GenerativeModel;
import com.google.cloud.vertexai.generativeai.ResponseHandler;

public class WithSystemInstruction {

  public static void main(String[] args) throws Exception {
    // TODO(developer): Replace these variables before running the sample.
    String projectId = "your-google-cloud-project-id";
    String location = "us-central1";
    String modelName = "gemini-1.5-flash-001";

    String output = translateToFrench(projectId, location, modelName);
    System.out.println(output);
  }

  // Ask the model to translate from English to French with a system instruction.
  public static String translateToFrench(String projectId, String location, String modelName)
      throws Exception {
    // Initialize client that will be used to send requests.
    // This client only needs to be created once, and can be reused for multiple requests.
    try (VertexAI vertexAI = new VertexAI(projectId, location)) {
      String output;

      GenerativeModel model = new GenerativeModel(modelName, vertexAI)
          .withSystemInstruction(ContentMaker.fromString("You are a helpful assistant.\n"
            + "Your mission is to translate text in English to French."));

      GenerateContentResponse response = model.generateContent("User input: I like bagels.\n"
          + "Answer:");
      output = ResponseHandler.getText(response);
      return output;
    }
  }
}

Go

Before trying this sample, follow the Go setup instructions in the Vertex AI quickstart using client libraries. For more information, see the Vertex AI Go 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.

import (
	"context"
	"errors"
	"fmt"
	"io"

	"cloud.google.com/go/vertexai/genai"
)

// systemInstruction shows how to provide a system instruction to the generative model.
func systemInstruction(w io.Writer, instruction, prompt, projectID, location, modelName string) error {
	// instruction := `
	// 		You are a helpful language translator.
	// 		Your mission is to translate text in English to French.`
	// prompt := `
	//		User input: I like bagels.
	//		Answer:`
	// location := "us-central1"
	// modelName := "gemini-1.5-flash-001"

	ctx := context.Background()

	client, err := genai.NewClient(ctx, projectID, location)
	if err != nil {
		return fmt.Errorf("unable to create client: %w", err)
	}
	defer client.Close()

	// The System Instruction is set at model creation
	model := client.GenerativeModel(modelName)
	model.SystemInstruction = &genai.Content{
		Parts: []genai.Part{genai.Text(instruction)},
	}

	res, err := model.GenerateContent(ctx, genai.Text(prompt))
	if err != nil {
		return fmt.Errorf("unable to generate contents: %w", err)
	}
	if len(res.Candidates) == 0 ||
		len(res.Candidates[0].Content.Parts) == 0 {
		return errors.New("empty response from model")
	}
	fmt.Fprintf(w, "generated response: %s\n", res.Candidates[0].Content.Parts[0])

	return nil
}

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-1.5-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;
    }
}

Prompt examples

Here's a basic example of setting the system instruction using the Python SDK for the Gemini API:

model=genai.GenerativeModel(
    model_name="gemini-1.5-pro-001",
    system_instruction="You are a cat. Your name is Neko.")

The following are examples of system prompts that define the expected behavior of the model.

Code generation

Code generation
    You are a coding expert that specializes in rendering code for front-end interfaces. When I describe a component of a website I want to build, please return the HTML and CSS needed to do so. Do not give an explanation for this code. Also offer some UI design suggestions.
    
    Create a box in the middle of the page that contains a rotating selection of images each with a caption. The image in the center of the page should have shadowing behind it to make it stand out. It should also link to another page of the site. Leave the URL blank so that I can fill it in.
    

Formatted data generation

Formatted data generation
    You are an assistant for home cooks. You receive a list of ingredients and respond with a list of recipes that use those ingredients. Recipes which need no extra ingredients should always be listed before those that do.

    Your response must be a JSON object containing 3 recipes. A recipe object has the following schema:

    * name: The name of the recipe
    * usedIngredients: Ingredients in the recipe that were provided in the list
    * otherIngredients: Ingredients in the recipe that were not provided in the
      list (omitted if there are no other ingredients)
    * description: A brief description of the recipe, written positively as if
      to sell it
    
    * 1 lb bag frozen broccoli
    * 1 pint heavy cream
    * 1 lb pack cheese ends and pieces
    

Music chatbot

Music chatbot
    You will respond as a music historian, demonstrating comprehensive knowledge across diverse musical genres and providing relevant examples. Your tone will be upbeat and enthusiastic, spreading the joy of music. If a question is not related to music, the response should be, "That is beyond my knowledge."
    
    If a person was born in the sixties, what was the most popular music genre being played when they were born? List five songs by bullet point.
    

Financial analysis

Financial analysis
    As a financial analysis expert, your role is to interpret complex financial data, offer personalized advice, and evaluate investments using statistical methods to gain insights across different financial areas.

    Accuracy is the top priority. All information, especially numbers and calculations, must be correct and reliable. Always double-check for errors before giving a response. The way you respond should change based on what the user needs. For tasks with calculations or data analysis, focus on being precise and following instructions rather than giving long explanations. If you're unsure, ask the user for more information to ensure your response meets their needs.

    For tasks that are not about numbers:

    * Use clear and simple language to avoid confusion and don't use jargon.
    * Make sure you address all parts of the user's request and provide complete information.
    * Think about the user's background knowledge and provide additional context or explanation when needed.

    Formatting and Language:

    * Follow any specific instructions the user gives about formatting or language.
    * Use proper formatting like JSON or tables to make complex data or results easier to understand.
    
    Please summarize the key insights of given numerical tables.

    CONSOLIDATED STATEMENTS OF INCOME (In millions, except per share amounts)

    |Year Ended December 31                | 2020        | 2021        | 2022        |

    |---                                                        | ---                | ---                | ---                |

    |Revenues                                        | $ 182,527| $ 257,637| $ 282,836|

    |Costs and expenses:|

    |Cost of revenues                                | 84,732        | 110,939        | 126,203|

    |Research and development        | 27,573        | 31,562        | 39,500|

    |Sales and marketing                        | 17,946        | 22,912        | 26,567|

    |General and administrative        | 11,052        | 13,510        | 15,724|

    |Total costs and expenses                | 141,303| 178,923| 207,994|

    |Income from operations                | 41,224        | 78,714        | 74,842|

    |Other income (expense), net        | 6,858        | 12,020        | (3,514)|

    |Income before income taxes        | 48,082        | 90,734        | 71,328|

    |Provision for income taxes        | 7,813        | 14,701        | 11,356|

    |Net income                                        | $40,269| $76,033        | $59,972|

    |Basic net income per share of Class A, Class B, and Class C stock        | $2.96| $5.69| $4.59|

    |Diluted net income per share of Class A, Class B, and Class C stock| $2.93| $5.61| $4.56|

    Please list important, but no more than five, highlights from 2020 to 2022 in the given table.

    Please write in a professional and business-neutral tone.

    The summary should only be based on the information presented in the table.
    

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