---
title: LangChain
description: Agentic adapter for the LangChain JS SDK.
---

- package: `@agentic/langchain`
- exports: `function createLangChainTools`
- [source](https://github.com/transitive-bullshit/agentic/blob/main/packages/langchain/src/langchain.ts)
- [LangChain JS docs](https://js.langchain.com)

## Install

<CodeGroup>
```bash npm
npm install @agentic/langchain @langchain/core langchain
```

```bash yarn
yarn add @agentic/langchain @langchain/core langchain
```

```bash pnpm
pnpm add @agentic/langchain @langchain/core langchain
```

</CodeGroup>

## Usage

```ts
import { createLangChainTools } from '@agentic/langchain'
import { WeatherClient } from '@agentic/stdlib'
import { ChatPromptTemplate } from '@langchain/core/prompts'
import { ChatOpenAI } from '@langchain/openai'
import { AgentExecutor, createToolCallingAgent } from 'langchain/agents'

async function main() {
  const weather = new WeatherClient()

  const tools = createLangChainTools(weather)
  const agent = createToolCallingAgent({
    llm: new ChatOpenAI({ model: 'gpt-4o-mini', temperature: 0 }),
    tools,
    prompt: ChatPromptTemplate.fromMessages([
      ['system', 'You are a helpful assistant. Be as concise as possible.'],
      ['placeholder', '{chat_history}'],
      ['human', '{input}'],
      ['placeholder', '{agent_scratchpad}']
    ])
  })

  const agentExecutor = new AgentExecutor({
    agent,
    tools
    // verbose: true
  })

  const result = await agentExecutor.invoke({
    input: 'What is the weather in San Francisco?'
  })

  console.log(result.output)
}

await main()
```

## Running this example

<Info>
  You'll need a free API key from [weatherapi.com](https://www.weatherapi.com)
  to run this example. Store it in a local `.env` file as `WEATHER_API_KEY`.
</Info>

<Info>
  You'll need an [OpenAI API key](https://platform.openai.com/docs/quickstart)
  to run this example. Store it in a local `.env` file as `OPENAI_API_KEY`.
</Info>

```sh
git clone git@github.com:transitive-bullshit/agentic.git
cd agentic
pnpm install
echo 'WEATHER_API_KEY=your-key' >> .env
echo 'OPENAI_API_KEY=your-key' >> .env
npx tsx examples/langchain/bin/weather.ts
```
