tltr MCP Server on Cloudflare Workers

index.ts

import { McpAgent } from "agents/mcp";
import { McpServer } from "@modelcontextprotocol/sdk/server/mcp.js";
import { z } from "zod";
import { GoogleGenerativeAI } from "@google/generative-ai";
import { Readability } from '@mozilla/readability';
import { parseHTML } from 'linkedom';

type Env = {
	MyMCP: DurableObjectNamespace<MyMCP>;
	GEMINI_API_KEY: string;
};

type State = {};

export class MyMCP extends McpAgent<Env, State, {}> {
	server = new McpServer({
		name: "tltr MCP Server",
		description: "Summarize lengthy articles. Fetch content from a URL and provide a concise summary.",
		version: "1.0.0",
	});

	initialState: State = {};

	async init() {
		this.server.tool(
			"tltr",
			"Summarize lengthy articles. Fetch content from a URL and provide a concise summary.",
			{ url: z.string().url() },
			async ({ url }) => {
				try {
					const response = await fetch(url);
					if (!response.ok) {
						throw new Error(`Failed to fetch URL: ${response.statusText}`);
					}
					const html = await response.text();
					const textContent = extractTextFromHTML(html);
					if (!textContent) {
						return { content: [{ type: "text", text: "Could not extract text content from the URL." }] };
					}
					const apiKey = this.env.GEMINI_API_KEY;
					const { pageTitle, summary } = await summarizeContent(textContent, apiKey);
					return {
						content: [
							{ type: "text", text: `**${pageTitle}**\n\n${summary}` },
						],
					};
				} catch (error) {
					console.error("Error in tltr tool:", error);
					const errorMessage = error instanceof Error ? error.message : String(error);
					return {
						content: [
							{ type: "text", text: `Error processing URL: ${errorMessage}` },
						],
					};
				}
			}
		);
	}

	onStateUpdate(state: State) {
		console.log({ stateUpdate: state });
	}
}

export default MyMCP.mount("/sse", {
	binding: "MyMCP",
})

export function extractTextFromHTML(html: string): string {
	try {
		const { document } = parseHTML(html);
		const reader = new Readability(document);
		const article = reader.parse();
		if (!article) return "";
		return `${article.title}\n\n${article.textContent}` || "";
	} catch (error) {
		console.error("Failed to extract content using Readability:", error);
		return "";
	}
}

export async function summarizeContent(content: string, apiKey: string): Promise<{ pageTitle: string, summary: string }> {
	if (!apiKey) throw new Error("Gemini API key not configured");

	const genAI = new GoogleGenerativeAI(apiKey);
	const systemInstruction = `Summarize the user's input.
## Instructions
- Start with a one-word conclusion.
- Then summarize the content in bullet points.
- Finally, generate a table of contents.

## Rules
- Start directly with the conclusion → summary without any preamble.
- Do not use headings like "Summary" in the response.
- Ensure no information is lost in the summary.
`;
	const generationConfig = {
		temperature: 0,
		topP: 0.95,
		topK: 40,
		maxOutputTokens: 4192,
		responseMimeType: "text/plain",
	};
	const model = genAI.getGenerativeModel({
		model: "gemini-2.5-pro-exp-03-25",
		systemInstruction,
		generationConfig
	});
	const result = await model.generateContent(content);
	const summaryText = result.response.text();
	const contentLines = content.split('\n');
	const potentialTitle = contentLines.length > 0 ? contentLines[0].trim() : "Summary";
	const pageTitle = potentialTitle || "Summary";
	const summary = summaryText.trim();

	return { pageTitle, summary };
}