Census Tigerweb MCP Server

@pipeworx/census-tigerweb

The Census Bureau's TIGERweb ArcGIS REST service: every TIGER/Line geography the Bureau publishes as a queryable layer — census tracts, block groups, 2020 blocks, ZCTAs, congressional and state legislative districts, school districts, tribal areas, places, counties, urban areas and PUMAs, with their GEOIDs, names, land/water area and interior points.

Part of Pipeworx — an MCP gateway connecting AI agents to 1683+ live data sources.

Tools

• tigerweb_list_layers(service?, filter?, include_label_layers?) — the queryable layers in a TIGERweb service. Call this first; layer ids move between vintages.
• tigerweb_query(layer_id, service?, where?, out_fields?, limit?, offset?, order_by?, return_geometry?) — ArcGIS WHERE-clause query against any layer.
• tigerweb_geography_at_point(latitude, longitude, service?, layers?) — every geography containing a coordinate, in one call.

Auth

Keyless.

Data sources

• https://tigerweb.geo.census.gov/arcgis/rest/services/TIGERweb/tigerWMS_Current/MapServer — current-vintage geography (default).
• https://tigerweb.geo.census.gov/arcgis/rest/services — the service directory, including ACS and Census2020 vintages.

Companion to census-geocoder: the geocoder maps an address to a tract, this pack lists and describes the geographies themselves.

Traps

• Half of the 80 layers in tigerWMS_Current are ... Labels layers — point annotation, not boundaries. Querying one returns rows that look like real geography. tigerweb_list_layers hides them unless asked.
• Layer numbers move between services and vintages. Never carry one over from another service.
• FIPS fields are zero-padded strings: STATE='11' matches, STATE=11 does not. A wrong-typed WHERE clause returns zero rows with a 200.
• ArcGIS errors on an outFields name a layer does not have, and these layers do not share a schema (Census Tracts has no BLOCK, ZCTAs have no COUNTY). tigerweb_geography_at_point asks for * and trims afterwards.
• resultRecordCount caps a page; the service has its own max too. Ask for more and you silently get the service max.
• Geometry is large — return_geometry defaults to false.

Quick Start

Add to your MCP client (Claude Desktop, Cursor, Windsurf, etc.):

{
  "mcpServers": {
    "census-tigerweb": {
      "url": "https://gateway.pipeworx.io/census-tigerweb/mcp"
    }
  }
}

What this endpoint actually serves

tools/list at https://gateway.pipeworx.io/census-tigerweb/mcp returns the tools in the table above plus the shared Pipeworx meta-tools — ask_pipeworx, discover_tools, search_within, remember/recall and the rest of the gateway-wide set. So the tool count you see is larger than this table: a single-pack endpoint currently lists roughly 30 shared tools alongside the pack's own. The connection's initialize response states its exact scope, and is the authoritative answer for a given day.

This is deliberate, not multiplexing by accident. The meta-tools are what let a scoped connection answer a question this pack does not cover — via ask_pipeworx, which routes across the whole catalog — without you adding a second MCP server. There is currently no way to mount a pack endpoint without them; if the extra schemas cost you more context than the routing is worth, connect to the full gateway once rather than to several pack endpoints.

Or connect to the full Pipeworx gateway to get every pack's tools listed directly, instead of just this one's:

{
  "mcpServers": {
    "pipeworx": {
      "url": "https://gateway.pipeworx.io/mcp"
    }
  }
}

Both URLs reach the same gateway and the same 1683+ data sources. The only difference is which pack's tools are listed directly; ask_pipeworx reaches all of them from either one.

No MCP client? Call it over HTTP

curl -X POST https://gateway.pipeworx.io/v1/tools/tigerweb_list_layers \
  -H 'Content-Type: application/json' \
  -d '{"filter":"school"}'

No account needed for the first calls. Inspect any tool: GET https://gateway.pipeworx.io/v1/tools/tigerweb_list_layers. Find one: POST https://gateway.pipeworx.io/v1/tools/search_packs with {"query":"..."}.

Standalone (no gateway account)

This package also runs as a local stdio MCP server — no Pipeworx account, no gateway round-trip:

{
  "mcpServers": {
    "census-tigerweb": {
      "command": "npx",
      "args": ["-y", "@pipeworx/mcp-census-tigerweb"]
    }
  }
}

Or run it directly to confirm it starts:

npx -y @pipeworx/mcp-census-tigerweb

It speaks MCP over stdin/stdout and answers initialize/tools/list/tools/call for only this pack's tools — none of the shared meta-tools the gateway connection above adds. Same source, same tools, no ask_pipeworx routing.

Using with ask_pipeworx

Instead of calling tools directly, you can ask questions in plain English — this works on the pack endpoint above as well as on the full gateway:

ask_pipeworx({ question: "your question about Census Tigerweb data" })

The gateway picks the right tool and fills the arguments automatically.

More

• Docs and guides
• pipeworx.io

License

MIT