Controlled generation JSON output with enum

Output JSON formatted object with an enum value, given a description of the object and a list of values to choose from.

Explore further

For detailed documentation that includes this code sample, see the following:

• Controlled generation

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.

public async Task<string> GenerateContentWithResponseSchema4(
    string projectId = "your-project-id",
    string location = "us-central1",
    string publisher = "google",
    string model = "gemini-1.5-pro-001")
{

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

    var responseSchema = new OpenApiSchema
    {
        Type = Type.Array,
        Items = new()
        {
            Type = Type.Object,
            Properties =
            {
                ["to_discard"] = new() { Type = Type.Integer },
                ["subcategory"] = new() { Type = Type.String },
                ["safe_handling"] = new() { Type = Type.Integer },
                ["item_category"] = new()
                {
                    Type = Type.String,
                    Enum =
                    {
                        "clothing",
                        "winter apparel",
                        "specialized apparel",
                        "furniture",
                        "decor",
                        "tableware",
                        "cookware",
                        "toys"
                    }
                },
                ["for_resale"] = new() { Type = Type.Integer },
                ["condition"] = new()
                {
                    Type = Type.String,
                    Enum =
                    {
                        "new in package",
                        "like new",
                        "gently used",
                        "used",
                        "damaged",
                        "soiled"
                    }
                }
            }
        }
    };

    string prompt = @"
        Item description:
        The item is a long winter coat that has many tears all around the seams and is falling apart.
        It has large questionable stains on it.";

    var generateContentRequest = new GenerateContentRequest
    {
        Model = $"projects/{projectId}/locations/{location}/publishers/{publisher}/models/{model}",
        Contents =
        {
            new Content
            {
                Role = "USER",
                Parts =
                {
                    new Part { Text = prompt }
                }
            }
        },
        GenerationConfig = new GenerationConfig
        {
            ResponseMimeType = "application/json",
            ResponseSchema = responseSchema
        },
    };

    GenerateContentResponse response = await predictionServiceClient.GenerateContentAsync(generateContentRequest);

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

    return responseText;
}

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"
)

// controlledGenerationResponseSchema4 shows how to make sure the generated output
// will always be valid JSON and adhere to a specific schema.
func controlledGenerationResponseSchema4(w io.Writer, projectID, location, modelName string) error {
	// location := "us-central1"
	// modelName := "gemini-1.5-pro-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()

	model := client.GenerativeModel(modelName)

	model.GenerationConfig.ResponseMIMEType = "application/json"

	// Build an OpenAPI schema, in memory
	model.GenerationConfig.ResponseSchema = &genai.Schema{
		Type: genai.TypeArray,
		Items: &genai.Schema{
			Type: genai.TypeObject,
			Properties: map[string]*genai.Schema{
				"to_discard":    {Type: genai.TypeInteger},
				"subcategory":   {Type: genai.TypeString},
				"safe_handling": {Type: genai.TypeString},
				"item_category": {
					Type: genai.TypeString,
					Enum: []string{
						"clothing",
						"winter apparel",
						"specialized apparel",
						"furniture",
						"decor",
						"tableware",
						"cookware",
						"toys",
					},
				},
				"for_resale": {Type: genai.TypeInteger},
				"condition": {
					Type: genai.TypeString,
					Enum: []string{
						"new in package",
						"like new",
						"gently used",
						"used",
						"damaged",
						"soiled",
					},
				},
			},
		},
	}

	prompt := `
		Item description:
		The item is a long winter coat that has many tears all around the seams and is falling apart.
		It has large questionable stains on it.
	`

	res, err := model.GenerateContent(ctx, genai.Text(prompt))
	if err != nil {
		return fmt.Errorf("unable to generate contents: %v", err)
	}

	if len(res.Candidates) == 0 ||
		len(res.Candidates[0].Content.Parts) == 0 {
		return errors.New("empty response from model")
	}

	fmt.Fprint(w, res.Candidates[0].Content.Parts[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.vertexai.VertexAI;
import com.google.cloud.vertexai.api.GenerateContentResponse;
import com.google.cloud.vertexai.api.GenerationConfig;
import com.google.cloud.vertexai.api.Schema;
import com.google.cloud.vertexai.api.Type;
import com.google.cloud.vertexai.generativeai.GenerativeModel;
import com.google.cloud.vertexai.generativeai.ResponseHandler;
import java.io.IOException;
import java.util.Arrays;

public class ControlledGenerationSchema4 {
  public static void main(String[] args) throws IOException {
    // TODO(developer): Replace these variables before running the sample.
    String projectId = "genai-java-demos";
    String location = "us-central1";
    String modelName = "gemini-1.5-pro-001";

    controlGenerationWithJsonSchema4(projectId, location, modelName);
  }

  // Generate responses that are always valid JSON and comply with a JSON schema
  public static String controlGenerationWithJsonSchema4(
      String projectId, String location, String modelName)
      throws IOException {
    // 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)) {
      Schema itemSchema = Schema.newBuilder()
          .setType(Type.OBJECT)
          .putProperties("to_discard", Schema.newBuilder().setType(Type.INTEGER).build())
          .putProperties("subcategory", Schema.newBuilder().setType(Type.STRING).build())
          .putProperties("safe_handling", Schema.newBuilder().setType(Type.INTEGER).build())
          .putProperties("item_category", Schema.newBuilder()
              .setType(Type.STRING)
              .addAllEnum(Arrays.asList(
                  "clothing", "winter apparel", "specialized apparel", "furniture",
                  "decor", "tableware", "cookware", "toys"))
              .build())
          .putProperties("for_resale", Schema.newBuilder().setType(Type.INTEGER).build())
          .putProperties("condition", Schema.newBuilder()
              .setType(Type.STRING)
              .addAllEnum(Arrays.asList(
                  "new in package", "like new", "gently used", "used", "damaged", "soiled"))
              .build())
          .build();

      GenerationConfig generationConfig = GenerationConfig.newBuilder()
          .setResponseMimeType("application/json")
          .setResponseSchema(Schema.newBuilder()
              .setType(Type.ARRAY)
              .setItems(itemSchema)
              .build())
          .build();

      GenerativeModel model = new GenerativeModel(modelName, vertexAI)
          .withGenerationConfig(generationConfig);

      GenerateContentResponse response = model.generateContent(
          "Item description:\n"
              + "The item is a long winter coat that has many tears all around the seams "
              + "and is falling apart.\n"
              + "It has large questionable stains on it."
      );

      String output = ResponseHandler.getText(response);
      System.out.println(output);
      return output;
    }
  }
}

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 GenerationConfig, GenerativeModel

# TODO(developer): Update and un-comment below line
# PROJECT_ID = "your-project-id"
vertexai.init(project=PROJECT_ID, location="us-central1")

response_schema = {
    "type": "ARRAY",
    "items": {
        "type": "OBJECT",
        "properties": {
            "to_discard": {"type": "INTEGER"},
            "subcategory": {"type": "STRING"},
            "safe_handling": {"type": "INTEGER"},
            "item_category": {
                "type": "STRING",
                "enum": [
                    "clothing",
                    "winter apparel",
                    "specialized apparel",
                    "furniture",
                    "decor",
                    "tableware",
                    "cookware",
                    "toys",
                ],
            },
            "for_resale": {"type": "INTEGER"},
            "condition": {
                "type": "STRING",
                "enum": [
                    "new in package",
                    "like new",
                    "gently used",
                    "used",
                    "damaged",
                    "soiled",
                ],
            },
        },
    },
}

prompt = """
    Item description:
    The item is a long winter coat that has many tears all around the seams and is falling apart.
    It has large questionable stains on it.
"""

model = GenerativeModel("gemini-1.5-pro-002")

response = model.generate_content(
    prompt,
    generation_config=GenerationConfig(
        response_mime_type="application/json", response_schema=response_schema
    ),
)

print(response.text)
# Example response:
# [
#     {
#         "condition": "damaged",
#         "item_category": "clothing",
#         "subcategory": "winter apparel",
#         "to_discard": 123,
#     }
# ]

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