gemini-3-pro-image (nano banana 2)

This document introduces the input and output parameters for the API of the gemini-3-pro-image-preview (Model ID: gemini-3-pro-image-preview) model. Use this for reference when utilizing the API.

Only some of the fields used are displayed below. For detailed explanations, please refer to the official documentation New Features in Gemini 3 Pro Image .

Request Parameters

Request Body

Field Name	Type	Required	Default Value	Description
contents	array	Required	-	The requested content, containing one or more parts.
contents.role	string	Required	”user”	The role of the content, fixed as “user” here.
contents.parts	array	Required	-	Specific parts of the content.
contents.parts.text	string	Optional	-	Prompt text.
generationConfig	object	Optional	-	Generation configuration.
generationConfig.responseModalities	array	Optional	[“TEXT”, “IMAGE”]	Desired response forms, either text or image.
generationConfig.imageConfig	object	Optional	-	Image generation configuration.
generationConfig.imageConfig.aspectRatio	string	Optional	”1:1”	Image aspect ratio. Supports “1:1”, “2:3”, “3:2”, “3:4”, “4:3”, “4:5”, “5:4”, “9:16”, “16:9”, “21:9”.
generationConfig.imageConfig.imageSize	string	Optional	”1K”	Image resolution. Supports “1K”, “2K”, “4K”.

Response Parameters

Field Name	Type	Description
candidates	`array`	List of returned candidate content.
candidates.content	`object`	Candidate content.
candidates.content.parts	`array`	Specific parts of content, may contain text and image data.
candidates.content.parts.text	`string`	Text description returned by the model.
candidates.content.parts.inlineData	`object`	Inline image data.
candidates.content.parts.inlineData.data	`string`	Base64-encoded image data.
candidates.content.parts.inlineData.mimeType	`string`	MIME type of data, e.g., “image/png”.
candidates.finishReason	`string`	Reason for generation ending, e.g., “STOP”.
usageMetadata	`object`	Metadata on token usage.
error	`Object`	Error information object.

Examples

Gemini Compatible Interface

POST https://api.umodelverse.ai/v1beta/models/gemini-3-pro-image-preview:generateContent

Image Generation (Text to Image)

⚠️ Note: You must include responseModalities: [“TEXT”, “IMAGE”] in the configuration.

curl


curl -s -X POST \
  "https://api.umodelverse.ai/v1beta/models/gemini-3-pro-image-preview:generateContent" \
  -H "x-goog-api-key: $MODELVERSE_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "contents": [{"parts": [{"text": "Da Vinci style anatomical sketch of a dissected Monarch butterfly. Detailed drawings of the head, wings, and legs on textured parchment with notes in English."}]}],
    "tools": [{"google_search": {}}],
    "generationConfig": {
      "responseModalities": ["TEXT", "IMAGE"],
      "imageConfig": {"aspectRatio": "1:1", "imageSize": "1K"}
    }
  }' | jq -r '.candidates[0].content.parts[] | select(.inlineData) | .inlineData.data' | head -1 | base64 --decode > butterfly.png

python


from google import genai
from google.genai import types
import os
 
client = genai.Client(
    api_key=os.getenv("MODELVERSE_API_KEY", "<MODELVERSE_API_KEY>"),  # Your API_KEY
    http_options=types.HttpOptions(
        base_url="https://api.umodelverse.ai"
    ),
)
 
prompt = "Da Vinci style anatomical sketch of a dissected Monarch butterfly. Detailed drawings of the head, wings, and legs on textured parchment with notes in English."
aspect_ratio = "1:1"  # "1:1","2:3","3:2","3:4","4:3","4:5","5:4","9:16","16:9","21:9"
resolution = "1K"  # "1K", "2K", "4K"
 
response = client.models.generate_content(
    model="gemini-3-pro-image-preview",
    contents=prompt,
    config=types.GenerateContentConfig(
        response_modalities=["TEXT", "IMAGE"],
        image_config=types.ImageConfig(
            aspect_ratio=aspect_ratio, image_size=resolution
        ),
    ),
)
 
for part in response.parts:
    if part.text is not None:
        print(part.text)
    elif image := part.as_image():
        image.save("butterfly.png")

Response Example


{
  "candidates": [
    {
      "content": {
        "parts": [
          {
            "text": "Here is the anatomical sketch of a dissected Monarch butterfly in Da Vinci style..."
          },
          {
            "inlineData": {
              "data": "iVBORw0KGgoAAAANSUhEUgAA...",
              "mimeType": "image/png"
            }
          }
        ],
        "role": "model"
      },
      "finishReason": "STOP"
    }
  ],
  "usageMetadata": {
    "candidatesTokenCount": 1315,
    "totalTokenCount": 1331
  }
}


{
  "error": {
    "message": "error_message",
    "type": "error_type",
    "param": "request_id",
    "code": "error_code"
  }
}