How to integrate Nextdns MCP with LangChain

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Introduction

This guide walks you through connecting Nextdns to LangChain using the Composio tool router. By the end, you'll have a working Nextdns agent that can block access to adult websites for a profile, download dns logs from last week, show top domains queried by my devices, clear all dns logs for my home profile through natural language commands.

This guide will help you understand how to give your LangChain agent real control over a Nextdns account through Composio's Nextdns MCP server.

Before we dive in, let's take a quick look at the key ideas and tools involved.

TL;DR

Here's what you'll learn:
  • Get and set up your OpenAI and Composio API keys
  • Connect your Nextdns project to Composio
  • Create a Tool Router MCP session for Nextdns
  • Initialize an MCP client and retrieve Nextdns tools
  • Build a LangChain agent that can interact with Nextdns
  • 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 Nextdns MCP server, and what's possible with it?

The Nextdns MCP server is an implementation of the Model Context Protocol that connects your AI agent and assistants like Claude, Cursor, etc directly to your Nextdns account. It provides structured and secure access to your DNS security and privacy controls, so your agent can perform actions like blocking domains, managing profiles, analyzing DNS analytics, and clearing logs on your behalf.

  • Dynamic domain and TLD blocking: Instantly add domains or top-level domains to your denylist or security blocklist, helping you stay ahead of new threats.
  • Profile management and configuration: Create, update, or delete NextDNS configuration profiles to tailor DNS filtering and security settings for different users or devices.
  • Comprehensive DNS analytics: Retrieve detailed analytics by device, domain, or client IP to monitor DNS activity, spot anomalies, and optimize security policies.
  • Log management and export: Download DNS query logs for audit or troubleshooting, or clear logs entirely to maintain your privacy.
  • Control over block page settings: Enable or disable the block page for any configuration, giving you flexibility over how blocks are displayed to users.

Supported Tools & Triggers

Tools
Add Blocked TLDTool to add a top-level domain to the security blocklist for a nextdns profile.
Add Denylist DomainTool to add a domain to the denylist of a nextdns profile.
Toggle Block PageTool to enable or disable block page for a configuration.
Clear LogsTool to clear dns logs for a nextdns profile.
Create ProfileThis tool allows users to create a new nextdns profile.
Delete NextDNS ConfigurationTool to delete a nextdns configuration profile.
Download LogsTool to download dns logs for a profile.
Get Analytics DevicesTool to retrieve analytics aggregated by devices.
Get Analytics DomainsTool to retrieve analytics data for domains within a specific profile.
Get Analytics IPsTool to retrieve analytics aggregated by client ip addresses.
Get Analytics IP VersionsTool to retrieve analytics grouped by ip version within a specific profile.
Get Analytics Query TypesTool to retrieve dns query counts broken down by query type.
Get Analytics ReasonsTool to retrieve dns query counts broken down by classification reason.
Get Analytics StatusTool to retrieve analytics status for a specific profile.
Get LogsTool to retrieve logs for a specific nextdns profile with optional filters.
Get Profile DetailsRetrieves the details of a specific nextdns profile.
Get Setup InfoTool to get setup information for a provided configuration (profile).
List ConfigurationsTool to list all configurations (profiles) available on the nextdns account.
List Denylist DomainsTool to list domains in the denylist for a profile.
List Security SettingsTool to list current security options for a nextdns configuration.
List SettingsTool to list settings for a nextdns profile.
Log Client IPsTool to enable or disable logging of client ips for a nextdns configuration.
Toggle Domain LoggingTool to enable or disable logging of domains for a nextdns profile.
NextDNS LoginTool to authenticate to the nextdns api.
Get Monthly QueriesTool to get the number of dns queries made in the current month for a profile.
Remove Blocked TLDTool to remove a top-level domain from the security blocklist for a nextdns profile.
Remove Denylist DomainTool to remove a domain from a profile's denylist.
Rename ConfigurationTool to rename a nextdns configuration (profile).
Set AI Threat DetectionTool to enable or disable ai threat detection for a nextdns configuration.
Toggle Cryptojacking ProtectionTool to enable or disable cryptojacking protection for a nextdns configuration.
Set CSAM BlockingTool to enable or disable blocking of child sexual abuse material domains for a nextdns profile.
Toggle DGA ProtectionTool to enable or disable dga (domain generation algorithm) protection for a nextdns configuration.
Set DNS Rebinding ProtectionTool to enable or disable dns rebinding protection for a nextdns configuration.
Set Homograph ProtectionTool to enable or disable homograph attack protection for a nextdns configuration.
Set Newly Registered DomainsTool to enable or disable blocking of newly registered domains for a nextdns profile.
Toggle Parked Domains BlockingTool to enable or disable blocking of parked domains for a nextdns configuration.
Set Safe BrowsingTool to enable or disable google safe browsing for a nextdns configuration.
Toggle Threat Intelligence FeedsTool to enable or disable real-time threat intelligence feeds for a nextdns configuration.
Toggle Typosquatting ProtectionTool to enable or disable typosquatting protection for a nextdns configuration.
Update linked IPTool to update the linked ip for a nextdns profile.
Update Performance SettingsTool to update performance settings of a nextdns profile.
Update Privacy SettingsTool to update privacy settings for a profile.
Update ProfileTool to update an existing profile.

What is the Composio tool router, and how does it fit here?

What is Tool Router?

Composio's Tool Router helps agents find the right tools for a task at runtime. You can plug in multiple toolkits (like Gmail, HubSpot, and GitHub), and the agent will identify the relevant app and action to complete multi-step workflows. This can reduce token usage and improve the reliability of tool calls. Read more here: Getting started with Tool Router

The tool router generates a secure MCP URL that your agents can access to perform actions.

How the Tool Router works

The Tool Router follows a three-phase workflow:

  1. Discovery: Searches for tools matching your task and returns relevant toolkits with their details.
  2. Authentication: Checks for active connections. If missing, creates an auth config and returns a connection URL via Auth Link.
  3. Execution: Executes the action using the authenticated connection.

Step-by-step Guide

Prerequisites

Before starting this tutorial, make sure you have:
  • Python 3.10 or higher installed on your system
  • A Composio account with an API key
  • An OpenAI API key
  • Basic familiarity with Python and async programming

Getting API Keys for OpenAI and Composio

OpenAI API Key
  • Go to the OpenAI dashboard 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.
  • Navigate to your API settings and generate a new API key.
  • Store this key securely as you'll need it for authentication.

Install dependencies

pip install composio-langchain langchain-mcp-adapters langchain python-dotenv

Install the required packages for LangChain with MCP support.

What's happening:

  • composio-langchain provides Composio integration for LangChain
  • langchain-mcp-adapters enables MCP client connections
  • langchain is the core agent framework
  • python-dotenv loads environment variables

Set up environment variables

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

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

Import dependencies

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()
What's happening:
  • We're importing LangChain's MCP adapter and Composio SDK
  • The dotenv import loads environment variables from your .env file
  • This setup prepares the foundation for connecting LangChain with Nextdns functionality through MCP

Initialize Composio client

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")
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 Nextdns tools
  • Validating that COMPOSIO_USER_ID is also set before proceeding

Create a Tool Router session

# Create Tool Router session for Nextdns
session = composio.create(
    user_id=os.getenv("COMPOSIO_USER_ID"),
    toolkits=['nextdns']
)

url = session.mcp.url
What's happening:
  • We're creating a Tool Router session that gives your agent access to Nextdns 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 Nextdns tools as needed

Configure the agent with the MCP URL

client = MultiServerMCPClient({
    "nextdns-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)
What's happening:
  • We're creating a MultiServerMCPClient that connects to our Nextdns MCP server via HTTP
  • The client is configured with a name and the URL from our Tool Router session
  • get_tools() retrieves all available Nextdns tools that the agent can use
  • We're creating a LangChain agent using the GPT-5 model

Set up interactive chat interface

conversation_history = []

print("Chat started! Type 'exit' or 'quit' to end the conversation.\n")
print("Ask any Nextdns 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")
What's happening:
  • We initialize an empty conversation_history list to maintain context across interactions
  • A while loop continuously accepts user input from the command line
  • When a user types a message, it's added to the conversation history and sent to the agent
  • The agent processes the request using the ainvoke() method with the full conversation history
  • Users can type 'exit', 'quit', or 'bye' to end the chat session gracefully

Run the application

if __name__ == "__main__":
    asyncio.run(main())
What's happening:
  • We call the main() function using asyncio.run() to start the application

Complete Code

Here's the complete code to get you started with Nextdns and LangChain:

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=['nextdns']
    )

    url = session.mcp.url
    
    client = MultiServerMCPClient({
        "nextdns-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 Nextdns 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())

Conclusion

You've successfully built a LangChain agent that can interact with Nextdns 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 Nextdns MCP Agent with another framework

OpenAI Agents SDK

OpenAI Agents SDK

Use Nextdns MCP with OpenAI Agents SDK

Claude Agent SDK

Claude Agent SDK

Use Nextdns MCP with Claude Agent SDK

Google ADK

Google ADK

Use Nextdns MCP with Google ADK

Vercel AI SDK

Vercel AI SDK

Use Nextdns MCP with Vercel AI SDK

Mastra AI

Mastra AI

Use Nextdns MCP with Mastra AI

LlamaIndex

LlamaIndex

Use Nextdns MCP with LlamaIndex

CrewAI

CrewAI

Use Nextdns MCP with CrewAI

FAQ

What are the differences in Tool Router MCP and Nextdns MCP?

With a standalone Nextdns MCP server, the agents and LLMs can only access a fixed set of Nextdns tools tied to that server. However, with the Composio Tool Router, agents can dynamically load tools from Nextdns 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 Nextdns tools.

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

Yes, absolutely. You can configure which Nextdns 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 Nextdns data and credentials are handled as safely as possible.

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