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Open Census

STDIO

MCP server providing natural language access to U.S. Census demographic data and statistics

Open Census MCP Server

Unofficial Project

Disclaimer

This is an independent, open-source experiment.
It is not affiliated with, endorsed by, or sponsored by the U.S. Census Bureau or the Department of Commerce.

Data retrieved through this project remains subject to the terms of the original data providers (e.g., Census API Terms of Service).

Stability

Container build 2.0 is decent, but still issues with the quality of results.

Census in Your Pocket 📱

Turn any AI assistant into your personal Census data expert. Ask questions in plain English, get accurate demographic data with proper interpretation and context.

Before: "I need ACS Table B19013 for FIPS code 24510 with margin of error calculations..."
After: "What's the median income in Baltimore compared to Maryland?"

🚀 Quick Start - Ready to Use!

Option 1: Pre-built Container (Recommended)

# Run the Census MCP server (one command - everything included!)
docker run -e CENSUS_API_KEY=your_key ghcr.io/brockwebb/census-mcp-server:latest

# Or without API key (still works, just slower rate limits)
docker run ghcr.io/brockwebb/census-mcp-server:latest

Claude Desktop Configuration

Add to your claude_desktop_config.json:

macOS: ~/Library/Application Support/Claude/claude_desktop_config.json
Windows: %APPDATA%\Claude\claude_desktop_config.json

{
  "mcpServers": {
    "census-mcp": {
      "command": "docker",
      "args": ["run", "--rm", "-i", "-e", "CENSUS_API_KEY=your_census_key", "ghcr.io/brockwebb/census-mcp-server:latest"]
    }
  }
}

That's it! Restart Claude Desktop and you'll see a 🔨 hammer icon indicating the Census tools are available.

Get a Census API Key (Optional but Recommended)

  1. Visit: https://api.census.gov/data/key_signup.html
  2. Register for a free API key (improves rate limits)
  3. Add to your Docker command or Claude Desktop config

Try It Out

Ask Claude questions like:

  • "What's the population of Austin, Texas?"
  • "Compare median income between California and Texas"
  • "What's the poverty rate in rural counties?"
  • "How do teacher salaries vary by state?" (it will correctly guide you to BLS data!)

The Problem

U.S. Census data is incredibly valuable but has a steep learning curve for non-specialists. Even experienced researchers struggle with geographic hierarchies, variable naming conventions, margin of error calculations, and knowing which data combinations actually work. In our experience, the biggest impediment to demographic analysis is often just figuring out how to get the right data in the first place.

Vision: Democratizing America's Data

Today: Census data influences billions in government spending and policy decisions, but accessing it effectively requires specialized knowledge that creates barriers for many potential users.

Opportunity: The semantic matching from natural language to Census variable codes is genuinely novel and could be transformative for researchers who currently have to navigate thousands of cryptic variable names manually. Everyone should have access to high-quality Census data with a world-class AI assistant.

Tomorrow: City council members fact-check claims in real-time during meetings. Journalists get demographic context while writing stories. Nonprofits understand their communities without hiring statisticians. Researchers spend time analyzing instead of wrestling with APIs.

The Goal: Make America's most valuable public dataset as easy to use as asking a question.

How It Works

graph LR
    A["User Question: Poverty rate in rural counties?"] --> B["AI Assistant (Claude, ChatGPT, etc.)"]
    B --> C["Census MCP Server (Domain Expertise Layer)"]
    C --> D["tidycensus R Package (Geography & Variable Resolution)"]
    C --> H["Knowledge Base (R Documentation + Census Methodology)"]
    D --> E["Census Bureau API (Official Data Source)"]
    H --> C
    E --> D
    D --> C
    C --> F["Interpreted Results + Context + Caveats"]
    F --> B
    B --> G["User gets accurate answer with proper interpretation"]
    
    style C fill:#e1f5fe
    style F fill:#f3e5f5

What's Included in the Container

🏗️ Complete Self-Contained System:

  • R environment with tidycensus, dplyr, and geospatial libraries
  • Python environment with MCP server and vector database
  • Pre-built knowledge base (85MB) with Census methodology and R documentation
  • All dependencies and configurations ready to go

📚 Built-in Intelligence:

  • Semantic Query Layer: Natural language → statistical concepts ("teacher salaries" → BLS guidance, "poverty" → proper Census variables)
  • 145+ pre-mapped demographic variables with fuzzy matching and concept expansion
  • Vector database with expert knowledge from Census methodology, R documentation, and statistical best practices
  • Smart geography parsing (handles "Austin, TX" → proper geographic codes, major city disambiguation)
  • Statistical guidance (when to use medians vs means, margin of error interpretation, survey limitations)
  • Power Law optimization: Core variables (<100ms) + comprehensive tidycensus fallback

🔄 No Setup Required:

  • No R installation needed
  • No Python environment configuration
  • No knowledge base building
  • No API wrestling

Example Use Cases

  • Basic Demographics: "Population of Miami-Dade County"
  • Comparative Analysis: "Compare unemployment rates between Detroit and Pittsburgh"
  • Housing Statistics: "How many renter-occupied units in Phoenix?"
  • Geographic Patterns: "Rural poverty rates across the Southeast"
  • Smart Routing: Ask about teacher salaries → guides you to BLS data instead of conflated Census categories

Architecture

The system consists of five main layers:

  1. AI Client Layer: Claude Desktop, Cursor, or other MCP-compatible assistants
  2. MCP Server (This Project): Domain expertise, query translation, result interpretation
  3. Knowledge Base: Vector database with R documentation and Census methodology
  4. Data Retrieval: tidycensus R package handling API communication and geography resolution
  5. Data Source Layer: Official U.S. Census Bureau APIs

Each layer handles its specialized function, creating a maintainable system that can evolve as both AI tools and Census data infrastructure change.

Current Scope: American Community Survey Focus

What Works Now:

  • American Community Survey (ACS) 5-year estimates
  • Demographics, economics, housing, social characteristics
  • Geographic resolution from national to place level
  • Proper statistical interpretation with margins of error

Future Expansion: Additional surveys, geographic visualizations, multi-agency integration

Technical Details

Built on: Model Context Protocol (MCP) for AI tool integration
Core Engine: tidycensus R package by Kyle Walker
Knowledge Base: ChromaDB vector database with sentence transformers
Container: ~4GB Docker image with all dependencies
Rate Limiting: Built-in throttling and caching strategies

Development Setup (Advanced Users)

If you want to modify or extend the system:

git clone https://github.com/brockwebb/census-mcp-server.git
cd census-mcp-server

# Build from source (requires R, Python, and substantial setup)
./build.sh

# Or use the pre-built container and modify as needed
docker run -v $(pwd):/workspace ghcr.io/brockwebb/census-mcp-server:latest

Acknowledgments

This project builds on exceptional work by:

  • Kyle Walker and the tidycensus R package - the gold standard for Census data access that handles the complex geography and API intricacies we rely on
  • Anthropic for the Model Context Protocol enabling seamless AI tool integration
  • The dedicated teams at the U.S. Census Bureau who collect and maintain this vital public data
  • The MCP community for building the ecosystem that makes this integration possible

Special thanks to Kyle Walker whose tidycensus documentation and methodology formed the foundation of our knowledge base. This project essentially wraps tidycensus with natural language intelligence - all the hard statistical and geographic work was solved by the tidycensus team.

Contributing

This project aims to democratize access to public data. We welcome contributions in:

  • Domain expertise improvements (especially from Census data veterans)
  • Additional geographic resolution and disambiguation
  • Statistical methodology implementation
  • Additional data source integration
  • Documentation and examples
  • Testing with real-world use cases

Roadmap

  • Phase 1: ACS 5-year estimates with natural language query translation
  • Phase 2: Containerized deployment with pre-built knowledge base
  • Phase 2.5: Semantic intelligence layer - variable concept mapping, statistical routing, RAG-enhanced responses
  • Phase 3: Performance optimization - semantic index for <100ms common queries, enhanced geographic disambiguation
  • Phase 4: Additional Census surveys (Economic Census, SIPP, PEP)
  • Phase 5: Multi-agency data integration (BLS employment, BEA economic data)
     RPC        DCE            RDF
      ↓          ↓              ↓ 
   CORBA       DCOM           OWL
      ↓          ↓              ↓
      └─→ SOAP ←┘            SPARQL
           ↓                   ↓
         REST           Knowledge Graphs
           ↓                   ↓
        GraphQL                ↓
           ↓                   ↓
          MCP ←─────────────→ LLMs

"The patterns never really die, they just get better UX"

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