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-contents, you-research, you-balance, and you-discover. To use you-finance, request it explicitly in the tools parameter.

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 provider (Anthropic, OpenAI, Google, Fireworks 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 APIs

Build your first LangChain agent in a few seconds

Use the ydc-langchain-integration skill to quickly integrate You.com tools with your LangChain.js application. This is the easiest and fastest way to get started. Install the skill and run it with your favorite coding agent.

npx skills add youdotcom-oss/agent-skills --skill ydc-langchain-integration

Once installed, run the skill directly or ask your AI agent: "Integrate LangChain.js with You.com tools"

Build your first LangChain agent manually instead

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-contents, you-research, you-balance, and you-discover) 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"
• "Compare the free cash flow of Apple, Microsoft, and Alphabet"

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-contents', 'you-research', 'you-balance', 'you-discover', '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-contents
• you-research
• you-balance
• you-discover

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-contents, you-research, you-finance, you-balance, you-discover, 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
const agent = createAgent({
  model: await initChatModel('claude-haiku-4-5'),
  tools,
});

// OpenAI
const agent = createAgent({
  model: await initChatModel('gpt-5-nano'),
  tools,
});

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-contents
• you-research
• you-balance
• you-discover

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)