How to integrate Census bureau MCP with LangChain

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Introduction

This guide walks you through connecting Census bureau to LangChain using the Composio tool router. By the end, you'll have a working Census bureau agent that can get latest population estimate for los angeles county, list top industries in texas by employment, fetch 5-year acs median income for chicago through natural language commands.

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

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

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TL;DR

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

The Census bureau MCP server is an implementation of the Model Context Protocol that connects your AI agent and assistants like Claude, Cursor, etc directly to Census Bureau data resources. It provides structured and secure access to a wide range of U.S. demographic, business, and community datasets, so your agent can retrieve population statistics, analyze survey results, fetch business patterns, and explore census variables on your behalf.

  • Retrieve up-to-date population estimates: Have your agent pull the latest demographic and population data for specific states, counties, or cities using the Population Estimates Program (PEP).
  • Analyze American Community Survey results: Access detailed ACS 1-year and 5-year estimates for any geography, helping you understand community trends, housing, and economic data.
  • Explore business statistics by region: Automatically fetch County Business Patterns (CBP) and Annual Business Survey (ABS) data to examine local industry and employment trends.
  • Access decennial census data: Let your agent retrieve variables and statistics from the decennial census by vintage and dataset for deep historical and demographic analysis.
  • Investigate variable metadata and definitions: Effortlessly obtain detailed information about any census variable, including descriptions, data types, and valid values for more informed analysis.

Supported Tools & Triggers

Tools
Geocode AddressTool to geocode a single address to get latitude/longitude coordinates.
Geocode Address for Census GeographiesGeocode an address and return Census geography identifiers including state, county, tract, block group, and block FIPS codes.
Geocode Address PartsTool to geocode an address using separate components (street, city, state, ZIP) to get latitude/longitude coordinates.
Geocode Address with GeographyTool to geocode an address and return both coordinates and Census geography information.
Geocode CoordinatesReverse geocode latitude/longitude coordinates to Census geographic areas.
Geocode Puerto Rico Address with GeographyTool to geocode a Puerto Rico address and return coordinates plus Census geography data.
Batch Geocode Addresses with GeographiesBatch geocode multiple addresses from a CSV file and return Census geography codes.
Geocode Puerto Rico AddressTool to geocode a Puerto Rico address with urbanization to latitude/longitude coordinates.
Get ACS 1-Year EstimatesTool to retrieve 1-year American Community Survey (ACS) estimates for a specified geography.
Get ACS 5-Year EstimatesRetrieve 5-year American Community Survey (ACS) estimates from the U.
Get Community Resilience EstimatesRetrieve U.
Get County Business PatternsTool to retrieve County Business Patterns (CBP) data for a specified year.
Get Dataset Examples HTMLTool to retrieve example queries for a Census dataset in HTML format.
Get Dataset Examples JSONTool to retrieve example API query patterns for a specific Census dataset and vintage.
Get Dataset Examples (XML)Tool to retrieve example queries for a Census Bureau dataset in XML format.
Get Dataset Geography HTMLTool to retrieve available geographies for a Census dataset in HTML format.
Get Dataset Geography JSONTool to get the list of supported geography levels for a specific Census dataset with their hierarchy and required predicates.
Get Dataset Geography XMLTool to retrieve available geographies for a Census Bureau dataset in XML format.
Get Dataset GroupsTool to retrieve the list of table groups for a Census dataset and vintage.
Get Dataset SortsTool to list available sort options for a specific Census dataset and vintage.
Get Dataset TagsTool to list available tags/keywords for a specific Census dataset and vintage.
Get Dataset Variables JSONTool to retrieve the complete list of available variables for a specific Census dataset.
Get Decennial Census DataRetrieve Decennial Census data (population, demographics, housing) from the U.
Get Planning Database DataGet Planning Database (PDB) data containing Census tract and block group level data useful for planning.
Get Population EstimatesRetrieves Population Estimates Program (PEP) data from the US Census Bureau API.
Get TIGERweb ACS Generalized BoundariesTool to access generalized ACS (American Community Survey) boundary services from TIGERweb for specific survey years (2012-2024).
Get TIGERweb Map Service MetadataTool to retrieve TIGERweb MapServer service metadata including available layers, capabilities, and spatial reference information.
Get Timeseries Examples HTMLTool to retrieve HTML-formatted example queries for a Census Bureau timeseries dataset.
Get Timeseries Examples JSONTool to get example queries for a timeseries dataset in JSON format.
Get Timeseries Examples XMLTool to retrieve example queries for a Census Bureau timeseries dataset in XML format.
Get Timeseries Geography HTMLTool to retrieve available FIPS geographies for a timeseries dataset in HTML format.
Get Timeseries Geography JSONTool to get available geographies for a timeseries dataset in JSON format.
Get Timeseries Geography XMLTool to retrieve available geographies for a Census Bureau timeseries dataset in XML format.
Get Timeseries Variables HTMLTool to retrieve a list of available variables for a Census timeseries dataset in HTML format.
Get Timeseries Variables JSONTool to get a list of variables available for a timeseries dataset in JSON format.
Get Timeseries Variables XMLTool to get a list of variables available for a timeseries dataset in XML format.
Get Variable DetailsTool to retrieve metadata for a specific variable in a Census dataset for a given year.
List Available DatasetsLists all available Census Bureau datasets with their metadata, vintages, and API endpoints.
List Datasets HTMLTool to retrieve a complete HTML listing of all available (non-timeseries) Census Bureau datasets.
List Datasets XMLTool to retrieve a list of all available Census Bureau datasets in XML format.
List Geocoder BenchmarksList all available benchmark versions for the Census Bureau geocoding service.
List Geocoder VintagesTool to list available geography vintages for a given Census geocoder benchmark.
List TIGERweb ServicesTool to discover all available TIGERweb map services for Census geographic boundaries.
List Timeseries Datasets (HTML)Tool to retrieve a list of all available timeseries datasets from the US Census Bureau API in HTML format.
List Timeseries Datasets (JSON)Tool to list all available timeseries datasets from the US Census Bureau API.
List Timeseries Datasets (XML)Tool to retrieve a list of all available Census Bureau timeseries datasets in XML format.
Query ACS Supplemental EstimatesQuery ACS Supplemental Estimates data by variables and geography.
Query ACS Comparison ProfilesQuery ACS Comparison Profiles data by variables and geography.
Query ACS Migration FlowsTool to query American Community Survey (ACS) Migration Flows data by variables and geography.
Query ACS Data ProfileTool to query ACS Data Profiles by variables and geography.
Query ACS Selected Population ProfilesTool to query ACS Selected Population Profiles (SPP) data by variables and geography for specific population groups.
Query ACS Subject TablesTool to query ACS Subject Tables data by variables and geography.
Query Annual Business SurveyTool to query Annual Business Survey Company Summary (abscs) data with demographic filters.
Query Commodity Flow SurveyQuery Commodity Flow Survey data on freight shipments by origin, destination, mode, and commodity.
Query CPS Survey DataTool to query Current Population Survey (CPS) microdata including basic monthly employment data and supplemental surveys.
Query Decennial DHCTool to query Decennial Census Demographic and Housing Characteristics (DHC) data by variables and geography.
Query Decennial Census Demographic ProfileTool to query Decennial Census Demographic Profile data by variables and geography.
Query Decennial Census P.L. Redistricting DataTool to query Decennial Census P.
Query Economic Census DataTool to query Economic Census data including establishments, employment, payroll, and receipts by geography and industry (NAICS).
Query International Trade TimeseriesTool to query International Trade timeseries data from Census Bureau API.
Query Nonemployer StatisticsTool to query Nonemployer Statistics data covering businesses with no paid employees.
Query PEP CharAgeGroupsQuery population estimates by age groups, sex, race, and Hispanic origin from the Census Bureau PEP CharAgeGroups dataset.
Query PEP ComponentsQuery components of population change from the Census Bureau Population Estimates Program (PEP).
Query PEP Housing EstimatesQuery housing unit estimates from the US Census Bureau Population Estimates Program (PEP).
Query Population ProjectionsQuery population projections from the Census Bureau API.
Query Surname DataQuery surname frequency data from the U.
Query TIGERweb LayerTool to query TIGERweb GeoServices for Census geographic boundaries and features.
Query Business Dynamics StatisticsQuery Business Dynamics Statistics (BDS) time series data from the Census Bureau.
Query Timeseries DataQuery Census timeseries datasets containing longitudinal data for multiple time periods.
Query Economic Indicators Time SeriesTool to query Economic Indicators Time Series (EITS) data from the US Census Bureau.
Query Residential Construction StatsTool to query Residential Construction statistics from Census Bureau Economic Indicators Time Series (EITS).
Query Residential Sales DataQuery Residential Sales statistics from Census Bureau's Economic Indicator Time Series (EITS).
Query Health Insurance EstimatesQuery Small Area Health Insurance Estimates (SAHIE) from the Census Bureau timeseries API.
Query Household Pulse Survey TimeseriesTool to query Household Pulse Survey (HPS) timeseries data measuring household experiences during the COVID-19 pandemic.
Query International DatabaseQuery International Database (IDB) demographic data for 227 countries and areas worldwide.
Query Timeseries International Trade Exports by HSTool to query international trade exports by Harmonized System code from Census Bureau time series API.
Query Timeseries International Trade Imports by End UseQuery international trade imports by end-use category from Census Bureau timeseries data.
Query Timeseries PovertyQuery poverty statistics from the Census Bureau's timeseries poverty datasets.
Query QWI Timeseries DataQuery Quarterly Workforce Indicators (QWI) timeseries data on employment, earnings, and job flows.
Query Timeseries QWI State/AreaQuery Quarterly Workforce Indicators (QWI) State/Area characteristics from the Census Bureau's time series API.
Query ZIP Business PatternsTool to query ZIP Code Business Patterns (ZBP) data including establishments and employment by ZIP code and industry.

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

What is Composio SDK?

Composio's Composio SDK 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 Composio SDK

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

How the Composio SDK works

The Composio SDK 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 Census bureau 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 Census bureau tools
  • Validating that COMPOSIO_USER_ID is also set before proceeding

Create a Tool Router session

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

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

Configure the agent with the MCP URL

client = MultiServerMCPClient({
    "census_bureau-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 Census bureau MCP server via HTTP
  • The client is configured with a name and the URL from our Tool Router session
  • get_tools() retrieves all available Census bureau 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 Census bureau 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 Census bureau 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=['census_bureau']
    )

    url = session.mcp.url
    
    client = MultiServerMCPClient({
        "census_bureau-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 Census bureau 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 Census bureau 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.

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FAQ

What are the differences in Tool Router MCP and Census bureau MCP?

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

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

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

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