# How to integrate Fixer MCP with LangChain

```json
{
  "title": "How to integrate Fixer MCP with LangChain",
  "toolkit": "Fixer",
  "toolkit_slug": "fixer",
  "framework": "LangChain",
  "framework_slug": "langchain",
  "url": "https://composio.dev/toolkits/fixer/framework/langchain",
  "markdown_url": "https://composio.dev/toolkits/fixer/framework/langchain.md",
  "updated_at": "2026-10-12T12:44:13.074Z"
}
```

## Introduction

This guide walks you through connecting Fixer to LangChain using the Composio tool router. By the end, you'll have a working Fixer agent that can get today's usd to eur exchange rate, show historical rates for gbp last week, list all supported currency symbols through natural language commands.
This guide will help you understand how to give your LangChain agent real control over a Fixer account through Composio's Fixer MCP server.
Before we dive in, let's take a quick look at the key ideas and tools involved.

## Also integrate Fixer with

- [Claude Code](https://composio.dev/toolkits/fixer/framework/claude-code)
- [Claude Cowork](https://composio.dev/toolkits/fixer/framework/claude-cowork)
- [OpenAI Agents SDK](https://composio.dev/toolkits/fixer/framework/open-ai-agents-sdk)
- [Claude Agent SDK](https://composio.dev/toolkits/fixer/framework/claude-agents-sdk)
- [Codex](https://composio.dev/toolkits/fixer/framework/codex)
- [Kimi Code](https://composio.dev/toolkits/fixer/framework/kimi)
- [OpenClaw](https://composio.dev/toolkits/fixer/framework/openclaw)
- [Hermes](https://composio.dev/toolkits/fixer/framework/hermes-agent)
- [Atomic Agent](https://composio.dev/toolkits/fixer/framework/atomic-agent)
- [CLI](https://composio.dev/toolkits/fixer/framework/cli)
- [Google ADK](https://composio.dev/toolkits/fixer/framework/google-adk)
- [Vercel AI SDK](https://composio.dev/toolkits/fixer/framework/ai-sdk)
- [Mastra AI](https://composio.dev/toolkits/fixer/framework/mastra-ai)
- [LlamaIndex](https://composio.dev/toolkits/fixer/framework/llama-index)
- [CrewAI](https://composio.dev/toolkits/fixer/framework/crew-ai)
- [Pydantic AI](https://composio.dev/toolkits/fixer/framework/pydantic-ai)
- [AutoGen](https://composio.dev/toolkits/fixer/framework/autogen)

## TL;DR

Here's what you'll learn:
- Get and set up your OpenAI and Composio API keys
- Connect your Fixer project to Composio
- Create a Tool Router MCP session for Fixer
- Initialize an MCP client and retrieve Fixer tools
- Build a LangChain agent that can interact with Fixer
- Set up an interactive chat interface for testing

## What is LangChain?

LangChain is a framework for developing applications powered by language models. It provides tools and abstractions for building agents that can reason, use tools, and maintain conversation context.
Key features include:
- Agent Framework: Build agents that can use tools and make decisions
- MCP Integration: Connect to external services through Model Context Protocol adapters
- Memory Management: Maintain conversation history across interactions
- Multi-Provider Support: Works with OpenAI, Anthropic, and other LLM providers

## What is the Fixer MCP server, and what's possible with it?

The Fixer MCP server is an implementation of the Model Context Protocol that connects your AI agent and assistants like Claude, Cursor, etc directly to your Fixer account. It provides structured and secure access to real-time and historical foreign exchange data, so your agent can fetch current rates, check past currency values, and look up supported symbols with ease.
- Live exchange rate retrieval: Instantly get the most up-to-date currency conversion rates for any supported global currency pair.
- Historical currency data access: Ask your agent to pull exchange rates for specific dates in the past, making trend analysis and financial reporting effortless.
- Supported currency symbol lookup: Quickly retrieve the full list of available currency codes and names to validate inputs or display options for users.
- Multi-currency comparisons: Let your agent fetch and compare rates across multiple currencies at once to power financial dashboards or conversion tools.

## Supported Tools

| Tool slug | Name | Description |
|---|---|---|
| `FIXER_GET_HISTORICAL_RATES` | Get Historical Rates | Tool to get historical exchange rate data for a specific date. Use when you need past currency rates for all or selected currencies. |
| `FIXER_GET_LATEST_RATES` | Get Latest Exchange Rates | Tool to get real-time exchange rate data for all available or specified currencies. Use when you need current forex rates before performing currency conversions. |
| `FIXER_GET_SUPPORTED_SYMBOLS` | Get Supported Symbols | Tool to retrieve all supported currency symbols and their full names. Use when you need to display or validate available currencies before performing conversions. |

## Supported Triggers

None listed.

## Creating MCP Server - Stand-alone vs Composio SDK

The Fixer MCP server is an implementation of the Model Context Protocol that connects your AI agent to Fixer. It provides structured and secure access so your agent can perform Fixer operations on your behalf through a secure, permission-based interface.
With Composio's managed implementation, you don't have to create your own developer app. For production, if you're building an end product, we recommend using your own credentials. The managed server helps you prototype fast and go from 0-1 faster.

## Step-by-step Guide

### 1. Prerequisites

No description provided.

### 1. Getting API Keys for OpenAI and Composio

OpenAI API Key
- Go to the [OpenAI dashboard](https://platform.openai.com/settings/organization/api-keys) and create an API key. You'll need credits to use the models, or you can connect to another model provider.
- Keep the API key safe.
Composio API Key
- Log in to the [Composio dashboard](https://dashboard.composio.dev?utm_source=toolkits&utm_medium=framework_docs).
- Navigate to your API settings and generate a new API key.
- Store this key securely as you'll need it for authentication.

### 2. Install dependencies

No description provided.
```python
pip install composio-langchain langchain-mcp-adapters langchain python-dotenv
```

```typescript
npm install @composio/langchain @langchain/core @langchain/openai @langchain/mcp-adapters dotenv
```

### 3. Set up environment variables

Create a .env file in your project root.
What's happening:
- COMPOSIO_API_KEY authenticates your requests to Composio's API
- COMPOSIO_USER_ID identifies the user for session management
- OPENAI_API_KEY enables access to OpenAI's language models
```bash
COMPOSIO_API_KEY=your_composio_api_key_here
COMPOSIO_USER_ID=your_composio_user_id_here
OPENAI_API_KEY=your_openai_api_key_here
```

### 4. Import dependencies

No description provided.
```python
from langchain_mcp_adapters.client import MultiServerMCPClient
from langchain.agents import create_agent
from dotenv import load_dotenv
from composio import Composio
import asyncio
import os

load_dotenv()
```

```typescript
import { Composio } from '@composio/core';
import { LangchainProvider } from '@composio/langchain';
import { MultiServerMCPClient } from "@langchain/mcp-adapters";
import { createAgent } from "langchain";
import * as readline from 'readline';
import 'dotenv/config';

dotenv.config();
```

### 5. Initialize Composio client

What's happening:
- We're loading the COMPOSIO_API_KEY from environment variables and validating it exists
- Creating a Composio instance that will manage our connection to Fixer tools
- Validating that COMPOSIO_USER_ID is also set before proceeding
```python
async def main():
    composio = Composio(api_key=os.getenv("COMPOSIO_API_KEY"))

    if not os.getenv("COMPOSIO_API_KEY"):
        raise ValueError("COMPOSIO_API_KEY is not set")
    if not os.getenv("COMPOSIO_USER_ID"):
        raise ValueError("COMPOSIO_USER_ID is not set")
```

```typescript
const composioApiKey = process.env.COMPOSIO_API_KEY;
const userId = process.env.COMPOSIO_USER_ID;

if (!composioApiKey) throw new Error('COMPOSIO_API_KEY is not set');
if (!userId) throw new Error('COMPOSIO_USER_ID is not set');

async function main() {
    const composio = new Composio({
        apiKey: composioApiKey as string,
        provider: new LangchainProvider()
    });
```

### 6. Create a Tool Router session

What's happening:
- We're creating a Tool Router session that gives your agent access to Fixer tools
- The create method takes the user ID and specifies which toolkits should be available
- The returned session.mcp.url is the MCP server URL that your agent will use
- This approach allows the agent to dynamically load and use Fixer tools as needed
```python
# Create Tool Router session for Fixer
session = composio.create(
    user_id=os.getenv("COMPOSIO_USER_ID"),
    toolkits=['fixer']
)

url = session.mcp.url
```

```typescript
const session = await composio.create(
    userId as string,
    {
        toolkits: ['fixer']
    }
);

const url = session.mcp.url;
```

### 7. Configure the agent with the MCP URL

No description provided.
```python
client = MultiServerMCPClient({
    "fixer-agent": {
        "transport": "streamable_http",
        "url": session.mcp.url,
        "headers": {
            "x-api-key": os.getenv("COMPOSIO_API_KEY")
        }
    }
})

tools = await client.get_tools()

agent = create_agent("gpt-5", tools)
```

```typescript
const client = new MultiServerMCPClient({
    "fixer-agent": {
        transport: "http",
        url: url,
        headers: {
            "x-api-key": process.env.COMPOSIO_API_KEY
        }
    }
});

const tools = await client.getTools();

const agent = createAgent({ model: "gpt-5", tools });
```

### 8. Set up interactive chat interface

No description provided.
```python
conversation_history = []

print("Chat started! Type 'exit' or 'quit' to end the conversation.\n")
print("Ask any Fixer related question or task to the agent.\n")

while True:
    user_input = input("You: ").strip()

    if user_input.lower() in ['exit', 'quit', 'bye']:
        print("\nGoodbye!")
        break

    if not user_input:
        continue

    conversation_history.append({"role": "user", "content": user_input})
    print("\nAgent is thinking...\n")

    response = await agent.ainvoke({"messages": conversation_history})
    conversation_history = response['messages']
    final_response = response['messages'][-1].content
    print(f"Agent: {final_response}\n")
```

```typescript
let conversationHistory: any[] = [];

console.log("Chat started! Type 'exit' or 'quit' to end the conversation.\n");
console.log("Ask any Fixer related question or task to the agent.\n");

const rl = readline.createInterface({
    input: process.stdin,
    output: process.stdout,
    prompt: 'You: '
});

rl.prompt();

rl.on('line', async (userInput: string) => {
    const trimmedInput = userInput.trim();

    if (['exit', 'quit', 'bye'].includes(trimmedInput.toLowerCase())) {
        console.log("\nGoodbye!");
        rl.close();
        process.exit(0);
    }

    if (!trimmedInput) {
        rl.prompt();
        return;
    }

    conversationHistory.push({ role: "user", content: trimmedInput });
    console.log("\nAgent is thinking...\n");

    const response = await agent.invoke({ messages: conversationHistory });
    conversationHistory = response.messages;

    const finalResponse = response.messages[response.messages.length - 1]?.content;
    console.log(`Agent: ${finalResponse}\n`);
        
        rl.prompt();
    });

    rl.on('close', () => {
        console.log('\n👋 Session ended.');
        process.exit(0);
    });
```

### 9. Run the application

No description provided.
```python
if __name__ == "__main__":
    asyncio.run(main())
```

```typescript
main().catch((err) => {
    console.error('Fatal error:', err);
    process.exit(1);
});
```

## Complete Code

```python
from langchain_mcp_adapters.client import MultiServerMCPClient
from langchain.agents import create_agent
from dotenv import load_dotenv
from composio import Composio
import asyncio
import os

load_dotenv()

async def main():
    composio = Composio(api_key=os.getenv("COMPOSIO_API_KEY"))
    
    if not os.getenv("COMPOSIO_API_KEY"):
        raise ValueError("COMPOSIO_API_KEY is not set")
    if not os.getenv("COMPOSIO_USER_ID"):
        raise ValueError("COMPOSIO_USER_ID is not set")
    
    session = composio.create(
        user_id=os.getenv("COMPOSIO_USER_ID"),
        toolkits=['fixer']
    )

    url = session.mcp.url
    
    client = MultiServerMCPClient({
        "fixer-agent": {
            "transport": "streamable_http",
            "url": url,
            "headers": {
                "x-api-key": os.getenv("COMPOSIO_API_KEY")
            }
        }
    })
    
    tools = await client.get_tools()
  
    agent = create_agent("gpt-5", tools)
    
    conversation_history = []
    
    print("Chat started! Type 'exit' or 'quit' to end the conversation.\n")
    print("Ask any Fixer related question or task to the agent.\n")
    
    while True:
        user_input = input("You: ").strip()
        
        if user_input.lower() in ['exit', 'quit', 'bye']:
            print("\nGoodbye!")
            break
        
        if not user_input:
            continue
        
        conversation_history.append({"role": "user", "content": user_input})
        print("\nAgent is thinking...\n")
        
        response = await agent.ainvoke({"messages": conversation_history})
        conversation_history = response['messages']
        final_response = response['messages'][-1].content
        print(f"Agent: {final_response}\n")

if __name__ == "__main__":
    asyncio.run(main())
```

```typescript
import { Composio } from '@composio/core';
import { LangchainProvider } from '@composio/langchain';
import { MultiServerMCPClient } from "@langchain/mcp-adapters";  
import { createAgent } from "langchain";
import * as readline from 'readline';
import 'dotenv/config';

const composioApiKey = process.env.COMPOSIO_API_KEY;
const userId = process.env.COMPOSIO_USER_ID;

if (!composioApiKey) throw new Error('COMPOSIO_API_KEY is not set');
if (!userId) throw new Error('COMPOSIO_USER_ID is not set');

async function main() {
    const composio = new Composio({
        apiKey: composioApiKey as string,
        provider: new LangchainProvider()
    });

    const session = await composio.create(
        userId as string,
        {
            toolkits: ['fixer']
        }
    );

    const url = session.mcp.url;
    
    const client = new MultiServerMCPClient({
        "fixer-agent": {
            transport: "http",
            url: url,
            headers: {
                "x-api-key": process.env.COMPOSIO_API_KEY
            }
        }
    });
    
    const tools = await client.getTools();
  
    const agent = createAgent({ model: "gpt-5", tools });
    
    let conversationHistory: any[] = [];
    
    console.log("Chat started! Type 'exit' or 'quit' to end the conversation.\n");
    console.log("Ask any Fixer related question or task to the agent.\n");
    
    const rl = readline.createInterface({
        input: process.stdin,
        output: process.stdout,
        prompt: 'You: '
    });

    rl.prompt();

    rl.on('line', async (userInput: string) => {
        const trimmedInput = userInput.trim();
        
        if (['exit', 'quit', 'bye'].includes(trimmedInput.toLowerCase())) {
            console.log("\nGoodbye!");
            rl.close();
            process.exit(0);
        }
        
        if (!trimmedInput) {
            rl.prompt();
            return;
        }
        
        conversationHistory.push({ role: "user", content: trimmedInput });
        console.log("\nAgent is thinking...\n");
        
        const response = await agent.invoke({ messages: conversationHistory });
        conversationHistory = response.messages;
        
        const finalResponse = response.messages[response.messages.length - 1]?.content;
        console.log(`Agent: ${finalResponse}\n`);
        
        rl.prompt();
    });

    rl.on('close', () => {
        console.log('\nSession ended.');
        process.exit(0);
    });
}

main().catch((err) => {
    console.error('Fatal error:', err);
    process.exit(1);
});
```

## Conclusion

You've successfully built a LangChain agent that can interact with Fixer through Composio's Tool Router.
Key features of this implementation:
- Dynamic tool loading through Composio's Tool Router
- Conversation history maintenance for context-aware responses
- Async Python provides clean, efficient execution of agent workflows
You can extend this further by adding error handling, implementing specific business logic, or integrating additional Composio toolkits to create multi-app workflows.

## How to build Fixer MCP Agent with another framework

- [Claude Code](https://composio.dev/toolkits/fixer/framework/claude-code)
- [Claude Cowork](https://composio.dev/toolkits/fixer/framework/claude-cowork)
- [OpenAI Agents SDK](https://composio.dev/toolkits/fixer/framework/open-ai-agents-sdk)
- [Claude Agent SDK](https://composio.dev/toolkits/fixer/framework/claude-agents-sdk)
- [Codex](https://composio.dev/toolkits/fixer/framework/codex)
- [Kimi Code](https://composio.dev/toolkits/fixer/framework/kimi)
- [OpenClaw](https://composio.dev/toolkits/fixer/framework/openclaw)
- [Hermes](https://composio.dev/toolkits/fixer/framework/hermes-agent)
- [Atomic Agent](https://composio.dev/toolkits/fixer/framework/atomic-agent)
- [CLI](https://composio.dev/toolkits/fixer/framework/cli)
- [Google ADK](https://composio.dev/toolkits/fixer/framework/google-adk)
- [Vercel AI SDK](https://composio.dev/toolkits/fixer/framework/ai-sdk)
- [Mastra AI](https://composio.dev/toolkits/fixer/framework/mastra-ai)
- [LlamaIndex](https://composio.dev/toolkits/fixer/framework/llama-index)
- [CrewAI](https://composio.dev/toolkits/fixer/framework/crew-ai)
- [Pydantic AI](https://composio.dev/toolkits/fixer/framework/pydantic-ai)
- [AutoGen](https://composio.dev/toolkits/fixer/framework/autogen)

## Related Toolkits

- [Stripe](https://composio.dev/toolkits/stripe) - Stripe is a global online payments platform offering APIs for managing payments, customers, and subscriptions. Trusted by businesses for secure, efficient, and scalable payment processing worldwide.
- [44API](https://composio.dev/toolkits/44api) - 44API is an API service for validating VAT and tax identifiers and returning company details. Use it to verify business tax data and manage account IP whitelists quickly.
- [Airwallex](https://composio.dev/toolkits/airwallex) - Airwallex is a global financial platform providing business accounts, payments, payouts, FX, and cards. Built to simplify cross-border payments and streamline financial operations for businesses.
- [Aiwyn Tax MCP](https://composio.dev/toolkits/aiwyn_tax_mcp) - Aiwyn Tax MCP is a tax estimation service powered by Aiwyn's federal and state tax engine. It helps teams estimate tax outcomes without building tax calculation logic from scratch.
- [Alpaca](https://composio.dev/toolkits/alpaca) - Alpaca is a stock and crypto trading platform for commission-free trading, real-time market data, and algorithmic strategies. Use it to build brokerage apps, trading bots, and portfolio workflows with market connectivity.
- [Alpha vantage](https://composio.dev/toolkits/alpha_vantage) - Alpha Vantage is a financial data platform offering real-time and historical stock market APIs. Get instant, reliable access to equities, forex, and technical analysis data for smarter trading decisions.
- [Altoviz](https://composio.dev/toolkits/altoviz) - Altoviz is a cloud-based billing and invoicing platform for businesses. It streamlines online payments, expense tracking, and customizable invoice management.
- [Benzinga](https://composio.dev/toolkits/benzinga) - Benzinga provides real-time financial news and data APIs for market coverage. It helps you track breaking news and actionable market insights instantly.
- [Bigdata.com MCP](https://composio.dev/toolkits/bigdata_com_mcp) - Bigdata.com MCP provides grounded access to financial news, transcripts, filings, and entity intelligence. Ideal for building research workflows and generating timely market insights.
- [Billsby](https://composio.dev/toolkits/billsby) - Billsby is a subscription billing platform for managing customers, subscriptions, invoices, products, plans, usage counters, add-ons, and allowances. It helps SaaS and subscription teams automate billing operations without building complex billing logic from scratch.
- [Brex](https://composio.dev/toolkits/brex) - Brex provides corporate credit cards and spend management tailored for startups and tech businesses. It helps optimize company cash flow, streamline accounting, and accelerate business growth.
- [Cashfree Payments MCP](https://composio.dev/toolkits/cashfree_payments_mcp) - Cashfree Payments MCP is a merchant payments platform that handles collection, payouts, subscriptions, settlements, refunds, and identity verification. Simplifies merchant money lifecycle management with unified, API-driven workflows.
- [Chaser](https://composio.dev/toolkits/chaser) - Chaser is accounts receivable automation software that sends invoice reminders and helps businesses get paid faster. It streamlines the collections process to save time and improve cash flow.
- [Clarity AI MCP](https://composio.dev/toolkits/clarity_ai_mcp) - Clarity AI MCP is an MCP toolkit for simulating SFDR 2.0 fund classifications from a fund name, ISIN, or CUSIP. Use it to tap Clarity AI disclosure data and modeling without building custom sustainability-data workflows.
- [Clientary](https://composio.dev/toolkits/clientary) - Clientary is a platform for managing clients, invoices, projects, proposals, and more. It streamlines client work and saves you serious admin time.
- [Coinbase](https://composio.dev/toolkits/coinbase) - Coinbase is a platform for buying, selling, and storing cryptocurrency. It makes exchanging and managing crypto simple and secure for everyone.
- [Coinbase Agents MCP](https://composio.dev/toolkits/coinbase_agents_mcp) - Coinbase Agents MCP is Coinbase's managed toolkit exposing accounts, portfolios, orders, fills, and market data. Use it to let authorized agents inspect holdings, execute trades, perform transfers, and handle payments.
- [Coinbase Wallet MCP](https://composio.dev/toolkits/coinbase_wallet_mcp) - Coinbase Wallet MCP is Coinbase's wallet service for interacting with onchain accounts. Use it to give agents secure, structured access to inspect wallets and request onchain actions.
- [Coinranking](https://composio.dev/toolkits/coinranking) - Coinranking is a comprehensive cryptocurrency market data platform offering access to real-time coin prices, market caps, and historical data. Get accurate, up-to-date stats for thousands of digital assets in one place.
- [Coupa](https://composio.dev/toolkits/coupa) - Coupa is a business spend management platform for procurement, invoicing, and expenses. It helps organizations streamline purchasing, control costs, and gain complete visibility over financial operations.

## Frequently Asked Questions

### What are the differences in Tool Router MCP and Fixer MCP?

With a standalone Fixer MCP server, the agents and LLMs can only access a fixed set of Fixer tools tied to that server. However, with the Composio Tool Router, agents can dynamically load tools from Fixer and many other apps based on the task at hand, all through a single MCP endpoint.

### Can I use Tool Router MCP with LangChain?

Yes, you can. LangChain fully supports MCP integration. You get structured tool calling, message history handling, and model orchestration while Tool Router takes care of discovering and serving the right Fixer tools.

### Can I manage the permissions and scopes for Fixer while using Tool Router?

Yes, absolutely. You can configure which Fixer scopes and actions are allowed when connecting your account to Composio. You can also bring your own OAuth credentials or API configuration so you keep full control over what the agent can do.

### How safe is my data with Composio Tool Router?

All sensitive data such as tokens, keys, and configuration is fully encrypted at rest and in transit. Composio is SOC 2 Type 2 compliant and follows strict security practices so your Fixer data and credentials are handled as safely as possible.

---
[See all toolkits](https://composio.dev/toolkits) · [Composio docs](https://docs.composio.dev/llms.txt)