This guide explains how to integrate Refile’s PDF generation capabilities with LangChain.js in just a few lines of code. This integration allows LLMs to generate PDFs directly from markdown content as part of their response flow.

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Prerequisites

  • A refile API key (available from your refile dashboard)
  • Node.js project with LangChain.js installed
  • Basic familiarity with LangChain.js usage patterns

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Quick Start

  1. Install the dependencies:
npm install @langchain/openai @langchain/core zod
  1. Copy the refile tool code and use it with LangChain:
import { createRefileTool } from "./refileTool.js";
import { ChatOpenAI } from "@langchain/openai";
import { HumanMessage } from "@langchain/core/messages";

// Initialize the OpenAI chat model
const model = new ChatOpenAI({
	temperature: 0,
	modelName: "gpt-4o", // You can change to a different model as needed
	openAIApiKey: "<token>",
});

// Create the refile tool
const refileTool = createRefileTool("<token>");

// Bind the tool to the model
const llmWithTool = model.bindTools([refileTool]);

// Create a messages array to track conversation
const messages = [
	new HumanMessage(
		"Create a research report on the rainforests of the Amazon as a PDF. Include sections on biodiversity, conservation efforts, and threats. Reply with the URL."
	),
];

// Get the initial response from the model
const aiMessage = await llmWithTool.invoke(messages);
console.log("Initial AI response:", aiMessage);

// Add the AI's response to the messages
messages.push(aiMessage);

// Check if there are tool calls to execute
if (aiMessage.tool_calls && aiMessage.tool_calls.length > 0) {
	// Process each tool call
	for (const toolCall of aiMessage.tool_calls) {
		console.log(`Executing tool call: ${toolCall.name}`);

		// Execute the tool with the tool call
		const toolMessage = await refileTool.invoke(toolCall);

		// Add the tool result to the messages
		messages.push(toolMessage);
	}

	// Get the final response with the tool results
	const finalResponse = await llmWithTool.invoke(messages);
	console.log("Final response:", finalResponse);
} else {
	// No tool calls were made
	console.log("No tool calls were made.");
}
  1. Replace <token> with your refile API key and start generating PDFs!

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How It Works

The integration follows these steps:
  1. Create the tool: The createRefileTool function creates a LangChain-compatible tool that connects to the Refile API
  2. Bind the tool to the model: Use LangChain’s bindTools method to give the model access to the PDF generation capability
  3. Process tool calls: When the model decides to generate a PDF, it makes a tool call which your code executes
  4. Return results: The final result includes the URL of the generated PDF

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Customization Options

Want a different look? Just change these parameters when calling createRefileTool(): 
createRefileTool(
	"your-api-key",
	"basic", // theme: "modern", "basic"
	"right", // page numbers: "center", "right", "left", "none"
	"Letter" // page size: "A4", "Letter", "Legal", etc.
);
Remember to keep your API key safe by using environment variables in production and never exposing your key in client side code! For a detailed explanation of the API and all configuration options, visit the API reference.