LangChain.js Tools for You.com

Give your LangChain agents real-time access to the web through the hosted You.com MCP server. This package exposes an async createYouClient() helper that connects to https://api.you.com/mcp via @langchain/mcp-adapters and returns the underlying LangChain MCP client. By default, await client.getTools() resolves to the default hosted tool set: you-search, you-research, and you-contents.

Features

Build LangChain agents that can:

• Search the web in real-time - Access current information with advanced filtering (dates, sites, file types)
• Research - Comprehensive answers with cited sources, configurable effort (lite to exhaustive)
• Extract any webpage - Pull full content in markdown or HTML format
• Zero configuration - Works with any LangChain-compatible model (Anthropic, OpenAI, Google, and more)
• Hosted MCP transport - Connects directly to the You.com hosted MCP server
• Type-safe - Full TypeScript support for async tool initialization
• Production-ready - Built on You.com's enterprise search API

AI Agent Skills

For LangChain.js Integration: Use the ydc-langchain-integration skill to quickly integrate You.com tools with your LangChain.js applications.

# Install the LangChain.js integration skill
npx skills add youdotcom-oss/agent-skills --skill ydc-langchain-integration

Once installed, ask your AI agent: "Integrate LangChain.js with You.com tools"

Getting started

Get up and running in 4 quick steps:

1. Get your API key

Visit you.com/platform/api-keys to get your You.com API key. Keep this key secure - you'll need it for configuration.

2. Install the package

Choose your package manager:

# NPM
npm install @youdotcom-oss/langchain langchain

# Bun
bun add @youdotcom-oss/langchain langchain

# Yarn
yarn add @youdotcom-oss/langchain langchain

3. Add tools to your agent

Import createYouClient(), await the MCP-backed client, then resolve tools from that client for your LangChain agent:

import { createAgent, initChatModel } from 'langchain';
import * as z from 'zod';
import { createYouClient } from '@youdotcom-oss/langchain';

const client = await createYouClient({
  apiKey: process.env.YDC_API_KEY,
});
const tools = await client.getTools();

// Create a chat model
const model = await initChatModel('claude-haiku-4-5', {
  temperature: 0,
});

// Define the agent's behavior
const systemPrompt = `You are a helpful research assistant.
Be concise and informative. Always cite your sources.`;

// Structured response format using Zod schema
const responseFormat = z.object({
  summary: z.string().describe('A concise summary of the findings'),
  key_points: z.array(z.string()).describe('Key points from the results'),
  urls: z.array(z.string()).describe('Source URLs'),
});

// Create an agent with all three tools — it picks the right one automatically
const agent = createAgent({
  model,
  tools,
  systemPrompt,
  responseFormat,
});

const result = await agent.invoke({
  messages: [{ role: 'user', content: 'What are the latest developments in AI?' }],
});

console.log(result.structuredResponse);

createYouClient() returns the underlying MCP client. Call await client.getTools() to resolve the default hosted tool set (you-search, you-research, and you-contents) unless you scope it with tools, and call await client.close() when finished.

Set your You.com API key as an environment variable:

export YDC_API_KEY=your-api-key-here

Set your model provider credentials separately for whichever provider you use.

4. Test your setup

Ask your agent something that needs real-time information:

• "What are the latest developments in quantum computing?"
• "Research the pros and cons of WebAssembly vs JavaScript"
• "Extract and analyze the content from https://anthropic.com"

Your agent will automatically choose the right tool and return up-to-date, accurate answers.

What you can build

Your LangChain agents can now handle requests like these:

Research & information

Current events:

• "What's trending in AI research this week?"
• "Find the latest news about climate policy from the past month"

Technical documentation:

• "Search for TypeScript best practices on the official docs"
• "Find examples of using WebAssembly in production"

Content analysis & extraction

Documentation analysis:

• "Extract and summarize the main points from https://docs.example.com"
• "Get the pricing information from https://competitor.com/pricing"

Multi-page research:

• "Extract content from these 3 blog posts and compare their approaches"
• "Pull the documentation from these URLs and create a summary"

Configuration

The tools work out of the box with environment variables:

export YDC_API_KEY=your-api-key-here

Passing configuration directly

You can override the API key, request a specific hosted MCP profile, or scope the request to specific tool ids:

import { createYouClient } from '@youdotcom-oss/langchain';

const client = await createYouClient({
  apiKey: 'your-api-key-here',
  tools: ['you-search', 'you-contents'],
});

const tools = await client.getTools();

you-finance is not included in the default tool set. Request it explicitly with tools.

Lead with the smallest explicit form when you only want finance:

const client = await createYouClient({
  tools: 'you-finance',
});

const financeTools = await client.getTools();

If you want the default tools plus finance, request all of them explicitly:

const client = await createYouClient({
  tools: ['you-search', 'you-research', 'you-contents', 'you-finance'],
});

const tools = await client.getTools();

Use profile when you want the hosted server to resolve tools through a named profile instead:

const client = await createYouClient({
  profile: 'free',
});

const tools = await client.getTools();

Configuration type

export type YouClientConfig = {
  apiKey?: string;           // Defaults to YDC_API_KEY
  tools?: string | string[]; // Added as ?tools=...
  profile?: string;          // Added as ?profile=...
};

Tool selection

The package always connects to https://api.you.com/mcp.

The default hosted tool set is:

• you-search
• you-research
• you-contents

Optional tools:

• you-finance

you-finance is not included in the default tool set. Request it explicitly with tools.

tools scopes the visible tool set.

profile selects a hosted server profile. tools scopes which tools are visible. If profile is provided, it takes precedence over tools.

Today, profile: 'free' is a search-only mode. It overrides tools and does not expose you-research, you-contents, you-finance, or livecrawl.

Using different model providers

These tools work with any LangChain-compatible model via initChatModel:

import { createAgent, initChatModel } from 'langchain';
import { createYouClient } from '@youdotcom-oss/langchain';

const client = await createYouClient();
const tools = await client.getTools();

// Anthropic Claude
const agent = createAgent({
  model: await initChatModel('claude-haiku-4-5'),
  tools,
  systemPrompt: 'You are a helpful assistant.',
});

// OpenAI
const searchClient = await createYouClient({
  tools: 'you-search',
});
const searchTools = await searchClient.getTools();

const agent = createAgent({
  model: await initChatModel('gpt-4'),
  tools: searchTools,
  systemPrompt: 'You are a helpful assistant.',
});

Direct tool usage

You can also await the tool list and invoke a specific tool directly:

import { createYouClient } from '@youdotcom-oss/langchain';

const client = await createYouClient({
  tools: 'you-search',
});
const tools = await client.getTools();
const searchTool = tools.find((tool) => tool.name === 'you-search');
const result = await searchTool?.invoke({ query: 'AI news', count: 5 });
console.log(result);

Available tools

Default tools:

• you-search
• you-research
• you-contents

Optional tools:

• you-finance

Note: Your LangChain agent automatically selects the right tool based on the user's request. Tool metadata and schemas come from the hosted MCP server at runtime.

Troubleshooting

Problem: "YDC_API_KEY is required" error

Solution: Set your API key as an environment variable:

export YDC_API_KEY=your-api-key-here

Or pass it directly when creating tools:

const client = await createYouClient({ apiKey: 'your-api-key-here' });
const tools = await client.getTools();

Problem: Agent isn't using the tools

Solution: Make sure you're using createAgent from langchain, which automatically handles tool calling:

import { createAgent, initChatModel } from 'langchain';
import { createYouClient } from '@youdotcom-oss/langchain';

const client = await createYouClient();
const tools = await client.getTools();

const agent = createAgent({
  model: await initChatModel('claude-haiku-4-5'),
  tools,
  systemPrompt: 'You are a helpful assistant.',
});

Problem: Getting 401 authentication errors

Solution: Verify your API key is correct and properly set:

echo $YDC_API_KEY

Get a new API key at you.com/platform/api-keys if needed.

Problem: Getting rate limit errors (429)

Solution: You've hit the API rate limit. Wait a few minutes before retrying, or check your API usage at you.com/platform/api-keys.

Need more help?

• GitHub Issues: Report bugs
• Email Support: [email protected]

For contributors

Interested in contributing? We'd love your help!

Development setup: See root AGENTS.md for monorepo conventions.

Quick contribution steps:

1. Fork the repository
2. Create a feature branch following CONTRIBUTING.md conventions
3. Follow code style guidelines (Biome enforced)
4. Write tests for your changes
5. Run quality checks: bun run check && bun test
6. Submit a pull request with a clear description

License: MIT - see LICENSE for details

Author: You.com (https://you.com)