Send text prompt requests

Vertex AI lets you test prompts by using Vertex AI Studio in the Google Cloud console, the Vertex AI API, and the Vertex AI SDK for Python. This page shows you how to test text prompts by using any of these interfaces.

To learn more about prompt design for text, see Design text prompts.

Test text prompts

To test text prompts, choose one of the following methods.

REST

To test a text prompt by using the Vertex AI API, send a POST request to the publisher model endpoint.

Before using any of the request data, make the following replacements:

PROJECT_ID: Your project ID.
PROMPT: A prompt is a natural language request submitted to a language model to receive a response back. Prompts can contain questions, instructions, contextual information, examples, and text for the model to complete or continue. (Don't add quotes around the prompt here.)
TEMPERATURE: The temperature is used for sampling during response generation, which occurs when topP and topK are applied. Temperature controls the degree of randomness in token selection. Lower temperatures are good for prompts that require a less open-ended or creative response, while higher temperatures can lead to more diverse or creative results. A temperature of 0 means that the highest probability tokens are always selected. In this case, responses for a given prompt are mostly deterministic, but a small amount of variation is still possible.
If the model returns a response that's too generic, too short, or the model gives a fallback response, try increasing the temperature.
MAX_OUTPUT_TOKENS: Maximum number of tokens that can be generated in the response. A token is approximately four characters. 100 tokens correspond to roughly 60-80 words.
Specify a lower value for shorter responses and a higher value for potentially longer responses.
TOP_P: Top-P changes how the model selects tokens for output. Tokens are selected from the most (see top-K) to least probable until the sum of their probabilities equals the top-P value. For example, if tokens A, B, and C have a probability of 0.3, 0.2, and 0.1 and the top-P value is 0.5, then the model will select either A or B as the next token by using temperature and excludes C as a candidate.
Specify a lower value for less random responses and a higher value for more random responses.
TOP_K: Top-K changes how the model selects tokens for output. A top-K of 1 means the next selected token is the most probable among all tokens in the model's vocabulary (also called greedy decoding), while a top-K of 3 means that the next token is selected from among the three most probable tokens by using temperature.
For each token selection step, the top-K tokens with the highest probabilities are sampled. Then tokens are further filtered based on top-P with the final token selected using temperature sampling.

Specify a lower value for less random responses and a higher value for more random responses.

HTTP method and URL:

POST https://us-central1-aiplatform.googleapis.com/v1/projects/PROJECT_ID/locations/us-central1/publishers/google/models/text-bison:predict

Request JSON body:

{
  "instances": [
    { "prompt": "PROMPT"}
  ],
  "parameters": {
    "temperature": TEMPERATURE,
    "maxOutputTokens": MAX_OUTPUT_TOKENS,
    "topP": TOP_P,
    "topK": TOP_K
  }
}

To send your request, choose one of these options:

curl

Note: The following command assumes that you have logged in to the gcloud CLI with your user account by running gcloud init or gcloud auth login , or by using Cloud Shell, which automatically logs you into the gcloud CLI . You can check the currently active account by running gcloud auth list.

Save the request body in a file named request.json, and execute the following command:

curl -X POST \
     -H "Authorization: Bearer $(gcloud auth print-access-token)" \
     -H "Content-Type: application/json; charset=utf-8" \
     -d @request.json \
     "https://us-central1-aiplatform.googleapis.com/v1/projects/PROJECT_ID/locations/us-central1/publishers/google/models/text-bison:predict"

PowerShell

Note: The following command assumes that you have logged in to the gcloud CLI with your user account by running gcloud init or gcloud auth login . You can check the currently active account by running gcloud auth list.

Save the request body in a file named request.json, and execute the following command:

$cred = gcloud auth print-access-token
$headers = @{ "Authorization" = "Bearer $cred" }

Invoke-WebRequest `
    -Method POST `
    -Headers $headers `
    -ContentType: "application/json; charset=utf-8" `
    -InFile request.json `
    -Uri "https://us-central1-aiplatform.googleapis.com/v1/projects/PROJECT_ID/locations/us-central1/publishers/google/models/text-bison:predict" | Select-Object -Expand Content

You should receive a JSON response similar to the following.

Response

{
  "predictions": [
    {
      "content": "RESPONSE"
      "citationMetadata": {
        "citations": []
      },
      "safetyAttributes": {
        "scores": [],
        "blocked": false,
        "categories": []
      }
    }
  ],
  "metadata": {
    "tokenMetadata": {
      "inputTokenCount": {
        "totalBillableCharacters": ,
        "totalTokens": 
      },
      "outputTokenCount": {
        "totalBillableCharacters": ,
        "totalTokens": 
      }
    }
  }
}

Example text-bison curl command

MODEL_ID="text-bison"
PROJECT_ID=PROJECT_ID

curl \
-X POST \
-H "Authorization: Bearer $(gcloud auth print-access-token)" \
-H "Content-Type: application/json" \
https://us-central1-aiplatform.googleapis.com/v1/projects/${PROJECT_ID}/locations/us-central1/publishers/google/models/${MODEL_ID}:predict -d \
$'{
  "instances": [
    { "prompt": "Give me ten interview questions for the role of program manager." }
  ],
  "parameters": {
    "temperature": 0.2,
    "maxOutputTokens": 256,
    "topK": 40,
    "topP": 0.95
  }
}'

Python

To learn how to install or update the Vertex AI SDK for Python, see Install the Vertex AI SDK for Python. For more information, see the Python API reference documentation.

import vertexai

from vertexai.language_models import TextGenerationModel

# TODO(developer): Update and un-comment below line
# PROJECT_ID = "your-project-id"
vertexai.init(project=PROJECT_ID, location="us-central1")
parameters = {
    "temperature": 0.2,  # Temperature controls the degree of randomness in token selection.
    "max_output_tokens": 256,  # Token limit determines the maximum amount of text output.
    "top_p": 0.8,  # Tokens are selected from most probable to least until the sum of their probabilities equals the top_p value.
    "top_k": 40,  # A top_k of 1 means the selected token is the most probable among all tokens.
}

model = TextGenerationModel.from_pretrained("text-bison@002")
response = model.predict(
    "Give me ten interview questions for the role of program manager.",
    **parameters,
)
print(f"Response from Model: {response.text}")
# Example response:
# Response from Model:  1. **Tell me about your experience managing programs.**
# 2. **What are your strengths and weaknesses as a program manager?**
# 3. **What do you think are the most important qualities for a successful program manager?**
# ...

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"
	"fmt"
	"io"

	aiplatform "cloud.google.com/go/aiplatform/apiv1beta1"
	"cloud.google.com/go/aiplatform/apiv1beta1/aiplatformpb"
	"google.golang.org/api/option"
	"google.golang.org/protobuf/types/known/structpb"
)

// textPredict generates text with certain prompt and configurations.
func textPredict(w io.Writer, projectID, location, model string) error {
	ctx := context.Background()

	prompt := "Hello, say something nice."
	publisher := "google"
	parameters := map[string]interface{}{
		"temperature":     0.8,
		"maxOutputTokens": 256,
		"topP":            0.4,
		"topK":            40,
	}

	apiEndpoint := fmt.Sprintf("%s-aiplatform.googleapis.com:443", location)

	client, err := aiplatform.NewPredictionClient(ctx, option.WithEndpoint(apiEndpoint))
	if err != nil {
		fmt.Fprintf(w, "unable to create prediction client: %v", err)
		return err
	}
	defer client.Close()

	// PredictRequest requires an endpoint, instances, and parameters
	// Endpoint
	base := fmt.Sprintf("projects/%s/locations/%s/publishers/%s/models", projectID, location, publisher)
	url := fmt.Sprintf("%s/%s", base, model)

	// Instances: the prompt to use with the text model
	promptValue, err := structpb.NewValue(map[string]interface{}{
		"prompt": prompt,
	})
	if err != nil {
		fmt.Fprintf(w, "unable to convert prompt to Value: %v", err)
		return err
	}

	// Parameters: the model configuration parameters
	parametersValue, err := structpb.NewValue(parameters)
	if err != nil {
		fmt.Fprintf(w, "unable to convert parameters to Value: %v", err)
		return err
	}

	// PredictRequest: create the model prediction request
	req := &aiplatformpb.PredictRequest{
		Endpoint:   url,
		Instances:  []*structpb.Value{promptValue},
		Parameters: parametersValue,
	}

	// PredictResponse: receive the response from the model
	resp, err := client.Predict(ctx, req)
	if err != nil {
		fmt.Fprintf(w, "error in prediction: %v", err)
		return err
	}

	fmt.Fprintf(w, "text-prediction response: %v", resp.Predictions[0])
	return nil
}

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.aiplatform.v1.EndpointName;
import com.google.cloud.aiplatform.v1.PredictResponse;
import com.google.cloud.aiplatform.v1.PredictionServiceClient;
import com.google.cloud.aiplatform.v1.PredictionServiceSettings;
import com.google.protobuf.Value;
import com.google.protobuf.util.JsonFormat;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

public class PredictTextPromptSample {

  public static void main(String[] args) throws IOException {
    // TODO(developer): Replace these variables before running the sample.
    // Details of designing text prompts for supported large language models:
    // https://cloud.google.com/vertex-ai/docs/generative-ai/text/text-overview
    String instance =
        "{ \"prompt\": " + "\"Give me ten interview questions for the role of program manager.\"}";
    String parameters =
        "{\n"
            + "  \"temperature\": 0.2,\n"
            + "  \"maxOutputTokens\": 256,\n"
            + "  \"topP\": 0.95,\n"
            + "  \"topK\": 40\n"
            + "}";
    String project = "YOUR_PROJECT_ID";
    String location = "us-central1";
    String publisher = "google";
    String model = "text-bison@001";

    predictTextPrompt(instance, parameters, project, location, publisher, model);
  }

  // Get a text prompt from a supported text model
  public static void predictTextPrompt(
      String instance,
      String parameters,
      String project,
      String location,
      String publisher,
      String model)
      throws IOException {
    String endpoint = String.format("%s-aiplatform.googleapis.com:443", location);
    PredictionServiceSettings predictionServiceSettings =
        PredictionServiceSettings.newBuilder().setEndpoint(endpoint).build();

    // 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 (PredictionServiceClient predictionServiceClient =
        PredictionServiceClient.create(predictionServiceSettings)) {
      final EndpointName endpointName =
          EndpointName.ofProjectLocationPublisherModelName(project, location, publisher, model);

      // Initialize client that will be used to send requests. This client only needs to be created
      // once, and can be reused for multiple requests.
      Value.Builder instanceValue = Value.newBuilder();
      JsonFormat.parser().merge(instance, instanceValue);
      List<Value> instances = new ArrayList<>();
      instances.add(instanceValue.build());

      // Use Value.Builder to convert instance to a dynamically typed value that can be
      // processed by the service.
      Value.Builder parameterValueBuilder = Value.newBuilder();
      JsonFormat.parser().merge(parameters, parameterValueBuilder);
      Value parameterValue = parameterValueBuilder.build();

      PredictResponse predictResponse =
          predictionServiceClient.predict(endpointName, instances, parameterValue);
      System.out.println("Predict Response");
      System.out.println(predictResponse);
    }
  }
}

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.

/**
 * TODO(developer): Update these variables before running the sample.
 */
const PROJECT_ID = process.env.CAIP_PROJECT_ID;
const LOCATION = 'us-central1';
const PUBLISHER = 'google';
const MODEL = 'text-bison@001';
const aiplatform = require('@google-cloud/aiplatform');

// Imports the Google Cloud Prediction service client
const {PredictionServiceClient} = aiplatform.v1;

// Import the helper module for converting arbitrary protobuf.Value objects.
const {helpers} = aiplatform;

// Specifies the location of the api endpoint
const clientOptions = {
  apiEndpoint: 'us-central1-aiplatform.googleapis.com',
};

// Instantiates a client
const predictionServiceClient = new PredictionServiceClient(clientOptions);

async function callPredict() {
  // Configure the parent resource
  const endpoint = `projects/${PROJECT_ID}/locations/${LOCATION}/publishers/${PUBLISHER}/models/${MODEL}`;

  const prompt = {
    prompt:
      'Give me ten interview questions for the role of program manager.',
  };
  const instanceValue = helpers.toValue(prompt);
  const instances = [instanceValue];

  const parameter = {
    temperature: 0.2,
    maxOutputTokens: 256,
    topP: 0.95,
    topK: 40,
  };
  const parameters = helpers.toValue(parameter);

  const request = {
    endpoint,
    instances,
    parameters,
  };

  // Predict request
  const response = await predictionServiceClient.predict(request);
  console.log('Get text prompt response');
  console.log(response);
}

callPredict();

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.Collections.Generic;
using System.Linq;
using Value = Google.Protobuf.WellKnownTypes.Value;

public class PredictTextPromptSample
{
    public string PredictTextPrompt(
        string projectId = "your-project-id",
        string locationId = "us-central1",
        string publisher = "google",
        string model = "text-bison@001"
    )
    {
        // Initialize client that will be used to send requests.
        // This client only needs to be created
        // once, and can be reused for multiple requests.
        var client = new PredictionServiceClientBuilder
        {
            Endpoint = $"{locationId}-aiplatform.googleapis.com"
        }.Build();

        // Configure the parent resource
        var endpoint = EndpointName.FromProjectLocationPublisherModel(projectId, locationId, publisher, model);

        // Initialize request argument(s)
        var prompt = "Give me ten interview questions for the role of program manager.";

        var instanceValue = Value.ForStruct(new()
        {
            Fields =
            {
                ["prompt"] = Value.ForString(prompt)
            }
        });

        var instances = new List<Value>
        {
            instanceValue
        };

        var parameters = Value.ForStruct(new()
        {
            Fields =
            {
                { "temperature", new Value { NumberValue = 0.2 } },
                { "maxOutputTokens", new Value { NumberValue = 256 } },
                { "topP", new Value { NumberValue = 0.95 } },
                { "topK", new Value { NumberValue = 40 } }
            }
        });

        // Make the request
        var response = client.Predict(endpoint, instances, parameters);

        // Parse and return the content.
        var content = response.Predictions.First().StructValue.Fields["content"].StringValue;
        Console.WriteLine($"Content: {content}");
        return content;
    }
}

Ruby

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

require "google/cloud/ai_platform/v1"

##
# Vertex AI Predict Text Prompt
#
# @param project_id [String] Your Google Cloud project (e.g. "my-project")
# @param location_id [String] Your Processor Location (e.g. "us-central1")
# @param publisher [String] The Model Publisher (e.g. "google")
# @param model [String] The Model Identifier (e.g. "text-bison@001")
#
def predict_text_prompt project_id:, location_id:, publisher:, model:
  # Create the Vertex AI client.
  client = ::Google::Cloud::AIPlatform::V1::PredictionService::Client.new do |config|
    config.endpoint = "#{location_id}-aiplatform.googleapis.com"
  end

  # Build the resource name from the project.
  endpoint = client.endpoint_path(
    project: project_id,
    location: location_id,
    publisher: publisher,
    model: model
  )

  prompt = "Give me ten interview questions for the role of program manager."

  # Initialize the request arguments
  instance = Google::Protobuf::Value.new(
    struct_value: Google::Protobuf::Struct.new(
      fields: {
        "prompt" => Google::Protobuf::Value.new(
          string_value: prompt
        )
      }
    )
  )

  instances = [instance]

  parameters = Google::Protobuf::Value.new(
    struct_value: Google::Protobuf::Struct.new(
      fields: {
        "temperature" => Google::Protobuf::Value.new(number_value: 0.2),
        "maxOutputTokens" => Google::Protobuf::Value.new(number_value: 256),
        "topP" => Google::Protobuf::Value.new(number_value: 0.95),
        "topK" => Google::Protobuf::Value.new(number_value: 40)
      }
    )
  )

  # Make the prediction request
  response = client.predict endpoint: endpoint, instances: instances, parameters: parameters

  # Handle the prediction response
  puts "Predict Response"
  puts response
end

Console

To test a text prompt by using Vertex AI Studio in the Google Cloud console, perform the following steps:

In the Vertex AI section of the Google Cloud console, go to the Vertex AI Studio page.
Go to Vertex AI Studio
Click the Get started tab.
Click Text prompt.
Select the method for inputting your prompt:
- Freeform is recommended for zero-shot prompts or copy-pasting few-shot prompts.
- Structured is recommended for designing few-shot prompts in Vertex AI Studio.
Freeform

Enter your prompt in the Prompt text field.
Structured

The structured method for inputting prompts separates the components of a prompt into different fields:
- Context: Enter instructions for the task that you want the model to perform and include any contextual information for the model to reference.
- Examples: For few-shot prompts, add input-output examples that that exhibit the behavioral patterns for the model to imitate. Adding a prefix for example input and output is optional. If you choose to add prefixes, they should be consistent across all examples.
- Test: In the Input field, enter the input of the prompt that you want to get a response for. Adding a prefix for the test input and output is optional. If your examples have prefixes, the test should have the same prefixes.
Configure the model and parameters:
- Model: Select a text-bison or gemini-1.0-pro model.
- Temperature: Use the slider or textbox to enter a value for temperature.
  The temperature is used for sampling during response generation, which occurs when topP and topK are applied. Temperature controls the degree of randomness in token selection. Lower temperatures are good for prompts that require a less open-ended or creative response, while higher temperatures can lead to more diverse or creative results. A temperature of 0 means that the highest probability tokens are always selected. In this case, responses for a given prompt are mostly deterministic, but a small amount of variation is still possible.
  If the model returns a response that's too generic, too short, or the model gives a fallback response, try increasing the temperature.
- Token limit: Use the slider or textbox to enter a value for the max output limit.
  Maximum number of tokens that can be generated in the response. A token is approximately four characters. 100 tokens correspond to roughly 60-80 words.
  Specify a lower value for shorter responses and a higher value for potentially longer responses.
- Top-K: Use the slider or textbox to enter a value for top-K.
  Top-K changes how the model selects tokens for output. A top-K of 1 means the next selected token is the most probable among all tokens in the model's vocabulary (also called greedy decoding), while a top-K of 3 means that the next token is selected from among the three most probable tokens by using temperature.
  For each token selection step, the top-K tokens with the highest probabilities are sampled. Then tokens are further filtered based on top-P with the final token selected using temperature sampling.
  
  Specify a lower value for less random responses and a higher value for more random responses.
- Top-P: Use the slider or textbox to enter a value for top-P. Tokens are selected from most probable to the least until the sum of their probabilities equals the value of top-P. For the least variable results, set top-P to 0.
Click Submit.
Optional: To save your prompt to My prompts, click Save.
Optional: To get the Python code or a curl command for your prompt, click View code.

Stream response from text model

To view sample code requests and responses using the REST API, see Examples using the REST API.

To view sample code requests and responses using the Vertex AI SDK for Python, see Examples using Vertex AI SDK for Python.

What's next

Learn how to send Gemini chat prompt requests.
Learn how to test chat prompts.
Learn how to tune a foundation model.
Learn about responsible AI best practices and Vertex AI's safety filters.

Send text prompt requests

Test text prompts

REST

curl

PowerShell

Response

Example text-bison curl command

Python

Go

Java

Node.js

C#

Ruby

Console

Freeform

Structured

Stream response from text model

What's next