# HUD User (USPS Crosswalk) MCP > HUD User (USPS Crosswalk) MCP maps US ZIP codes to official Census Bureau boundaries. It provides crosswalks linking a simple 5-digit ZIP code to complex geographies like Tracts, Counties, CBSAs, and Congressional Districts. This is essential for accurate data processing in real estate, urban planning, or demographic research. ## Overview - **Category:** real-estate - **Price:** Free - **Tags:** census-data, urban-planning, geocoding, demographics, zip-code-mapping, public-records ## Description When you're working with location data, the biggest headache isn't getting the address; it’s figuring out which official boundaries that address actually falls into. A ZIP code is just a simplification, right? But for proper analysis—whether you're running market predictions or modeling demographic shifts—you need precision. This MCP connects to the HUD User Data API and gives your AI client all the necessary crosswalks in one place. You can map ZIP codes back to everything from Census Tracts and Counties to Core Based Statistical Areas (CBSAs) and even Congressional Districts. It's about going beyond the simple zip code look-up. If you need to analyze how certain urban areas correlate with county lines, or if you’re building a real estate tool that needs district-level data, this MCP handles the heavy lifting of geography. You can connect it through Vinkius and let your agent pull in all these official mapping layers without having to piece together ten different government APIs. It's raw power for people who need clean, reliable spatial data. ## Tools ### cbsa_to_zip Finds all the ZIP codes that belong within a specific Core Based Statistical Area (CBSA). ### cbsadiv_to_zip Retrieves all ZIP codes contained in a given CBSA Division. ### cd_to_zip Maps out every ZIP code located within a specific Congressional District. ### county_to_zip Lists all the ZIP codes that are part of a specified county. ### tract_to_zip Finds every ZIP code associated with a specific Census Tract. ### zip_to_cbsa Determines which Core Based Statistical Area (CBSA) a given ZIP code belongs to. ### zip_to_cbsadiv Maps a specific ZIP code to its corresponding CBSA Division. ### zip_to_cd Looks up the Congressional District that encompasses an input ZIP code. ### zip_to_county Maps a specific ZIP code directly to its county name and ID. ### zip_to_tract Identifies the precise Census Tract boundaries for any given ZIP code. ## Prompt Examples **Prompt:** ``` Find the census tracts associated with ZIP code 90210. ``` **Response:** ``` I'll retrieve the ZIP to Tract crosswalk for you. ``` **Prompt:** ``` Which ZIP codes are in county FIPS 06037? ``` **Response:** ``` I'll map that county FIPS to its corresponding ZIP codes. ``` **Prompt:** ``` Get the congressional districts for ZIP code 10001. ``` **Response:** ``` I'll look up the congressional districts for that ZIP code. ``` ## Capabilities ### Map ZIP codes to county boundaries Determines the precise county and Census Tract associated with any given five-digit ZIP code. ### Cross-reference large geographic areas Maps major statistical regions, like CBSAs or Congressional Districts, back to their corresponding ZIP codes. ### Identify demographic boundaries Links a specific ZIP code to its underlying Census Bureau divisions (CBSA Divisions and Tracts). ### Calculate state-level data points Retrieves county, district, or tract information necessary for high-level planning and reporting. ## Use Cases ### Analyzing Market Penetration by County A commercial team wants to see which markets in the Midwest fall under a specific county. They use `county_to_zip` first, generating hundreds of target ZIP codes. Then, they pass those results into an analysis tool that requires precise Census Tract boundaries for modeling. ### Building Voter Data Profiles A political consultant needs to build a profile based on voting history tied to Congressional Districts. They use `zip_to_cd` repeatedly across thousands of records, ensuring their entire dataset is correctly tagged with the required district ID. ### Cross-Referencing Census Data A university researcher needs to compare historical data (tied to Tracts) with current real estate listings. They use `zip_to_tract` on their list of modern ZIP codes, instantly aligning them with the old census boundaries. ### Determining Data Scope A government contractor receives a request to pull all data for an entire Core Based Statistical Area (CBSA). They use `cbsa_to_zip` to generate the master list of all required ZIP codes before running their main query. ## Benefits - Accurate County Mapping: Instead of guessing, use `zip_to_county` to guarantee the exact county for every ZIP code in your dataset. This eliminates costly data errors. - Deep Demographic Insight: Get granular detail with tools like `zip_to_tract`, which links a simple address to its specific Census Tract boundary—critical for detailed research. - Understanding Regional Groupings: Quickly map any ZIP code to its CBSA using `zip_to_cbsa` or find out what large areas contain it via `zip_to_cbsadiv`. Ideal for market segmentation. - Political Boundary Resolution: When you need to know which Congressional District a ZIP belongs to, just use `zip_to_cd`. No more manual lookups against election maps. - Reverse Lookups: Need to know what's inside a boundary? Use `county_to_zip` or `cbsa_to_zip` to generate comprehensive lists of all associated ZIP codes for large-area analysis. ## How It Works The bottom line is that it turns simple location codes into complex, officially verified geographic boundaries for any analysis. 1. You tell your AI client the starting point: a list of ZIP codes you need mapped. 2. The MCP sends these ZIP codes to the HUD User API, specifying which Census geography (e.g., County or Tract) you want to link them to. 3. Your agent receives a structured JSON output containing the full crosswalk data, linking every input ZIP code to its corresponding official boundary. ## Frequently Asked Questions **How do I map ZIP codes to Census Tracts using the `zip_to_tract` tool?** The MCP finds the precise Census Tract for any given ZIP code. You simply input your list of ZIP codes, and the tool returns the specific tract boundary data needed for granular analysis. **What is the difference between `zip_to_county` and `cbsa_to_zip`?** `zip_to_county` takes a ZIP code and tells you its single county. Conversely, `cbsa_to_zip` takes an entire Core Based Statistical Area (CBSA) and gives you every ZIP code that belongs to it. **Can I find all the CBSAs from one zip code using `zip_to_cbsa`?** Yes, running `zip_to_cbsa` directly maps the input ZIP code to its corresponding Core Based Statistical Area. This is a key step for broad market analysis. **Does `county_to_zip` work in reverse of `zip_to_county`?** Yes, it does. If you know the county name or code and need all associated ZIPs, use `county_to_zip`. This is useful for generating full lists for a region. **Before running `county_to_zip`, what authentication steps are needed?** You need an API key provided by HUD User. The MCP handles standard OAuth flows, securing access to all the crosswalk data points you request. **If I process thousands of ZIP codes using `zip_to_tract`, are there rate limits?** Yes, the underlying API imposes standard request throttling. For bulk processing, batching your requests or checking the HUD User developer documentation for specific commercial quotas is necessary. **When running `zip_to_cd`, what happens if a ZIP code isn't assigned to a congressional district?** The tool returns null or an error message indicating no match. Always check the returned data for empty values before processing those results in your application logic. **Can `cbsa_to_zip` provide demographic information, or just mapping?** This MCP is strictly a crosswalk tool; it only maps the geographic relationship. You receive the list of associated ZIP codes but must query other external services for population or income metrics. **How do I get a HUD User Access Token?** Register for an account at the HUD User API page (https://www.huduser.gov/portal/dataset/uspszip-api.html), confirm your email, and generate a token in your user dashboard. **Which year of data is used?** By default, the API returns the most recent available data. You can optionally specify a year and quarter in each tool. **Does it support mapping Tracts back to ZIP codes?** Yes, tools like tract_to_zip and county_to_zip allow bidirectional crosswalking between geography IDs and ZIP codes.