LangChain.js

Give your LLM agents the ability to generate and edit images with Decart.

The @decartai/langchain package provides a LangChain Tool that gives any LLM agent the ability to generate and edit images using Decart.

Prerequisites

• A Decart API key
• Node.js 18+
• An LLM provider (Anthropic, OpenAI, etc.) for agent usage

Installation

Install the package along with the required @langchain/core peer dependency:

npm

npm install @decartai/langchain @langchain/core

Setup

Set your Decart API key as an environment variable:

export DECART_API_KEY="your-api-key"

Get your API key from platform.decart.ai. See authentication for details.

Or pass your API key directly to the tool:

import { DecartImageTool } from '@decartai/langchain';

const tool = new DecartImageTool({ apiKey: 'your-api-key' });

Quick start

Text-to-image

Generate an image from a text prompt:

import { DecartImageTool } from '@decartai/langchain';

const tool = new DecartImageTool();

const image = await tool.invoke({
  prompt: 'A serene mountain landscape at sunset',
  resolution: '720p',
});
// Returns: data:image/png;base64,...

Image editing

Edit an existing image by providing an imageUrl:

const editedImage = await tool.invoke({
  prompt: 'Change the sky to aurora borealis',
  imageUrl: 'https://example.com/original.jpg',
});

The tool automatically selects the right model: lucy-pro-t2i for text-to-image (no imageUrl), and lucy-pro-i2i for image-to-image editing (with imageUrl).

Using with LLM agents

Bind the tool to an LLM to let it generate images on its own:

import { ChatAnthropic } from '@langchain/anthropic';
import { HumanMessage } from '@langchain/core/messages';
import { DecartImageTool } from '@decartai/langchain';

const llm = new ChatAnthropic({ model: 'claude-sonnet-4-20250514' });
const tool = new DecartImageTool();

const llmWithTools = llm.bindTools([tool]);

const response = await llmWithTools.invoke([
  new HumanMessage('Generate an image of a futuristic city at night'),
]);

if (response.tool_calls?.length > 0) {
  const result = await tool.invoke(response.tool_calls[0].args);
  console.log('Generated image:', result);
}

This works with any LangChain-compatible LLM that supports tool calling — including OpenAI, Google, and Mistral models.

Parameters

prompt · string · required

Text description for image generation, or an edit instruction for image-to-image.

resolution · "480p" | "720p" · default: "720p"

Output resolution.

orientation · "landscape" | "portrait"

Output orientation. Only applies to text-to-image generation.

seed · number

Seed value for reproducible results.

imageUrl · string

Source image URL for image-to-image editing. When provided, the tool uses lucy-pro-i2i instead of lucy-pro-t2i.

enhancePrompt · boolean · default: "true"

Automatically enhance the prompt for better results.

Model selection

The tool selects the model automatically based on your input:

Input	Model	Mode
prompt only	lucy-pro-t2i	Text-to-image generation
prompt + imageUrl	lucy-pro-i2i	Image-to-image editing

Constructor options

apiKey · string

Decart API key. Defaults to the DECART_API_KEY environment variable.

baseUrl · string

Custom API base URL.

Next steps

Models overview

Explore all available Decart models.

JavaScript SDK

Use Decart’s native SDK for full API access.

GitHub

View source code and contribute.