Hud

Hud Crosswalk

hud_crosswalk

Read-onlyIdempotent

Map ZIP codes to census tracts, counties, CBSAs, and congressional districts. Returns geographic identifiers. Use to translate between location code formats or join datasets.

Example tool call

This call uses example arguments supplied in the tool’s input schema.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "type": 1,
      "query": "90210"
    },
    "name": "hud_crosswalk"
  }
}

Input Schema

Name	Required	Description
`type`	Yes	Crosswalk type: 1=ZIP-to-tract, 2=ZIP-to-county, 3=ZIP-to-CBSA, 4=ZIP-to-congressional-district, 7=county-to-ZIP.
`query`	Yes	Input value: ZIP code (for types 1-4), or FIPS county code (for type 7). Example: "90210" or "06037".
`_apiKey`	Yes	HUD API token

Output Schema

Name	Required	Description
`data`	Yes	Geographic crosswalk mapping data from HUD API
`query`	Yes	Input query value provided in request
`crosswalk_type`	Yes	Human-readable crosswalk type label

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedSep 24, 2026

changedInput schema / examples

Previous value: -[
-  {
-    "_apiKey": "your-hud-api-key",
-    "query": "90210",
-    "type": 1
-  },
-  {
-    "_apiKey": "your-hud-api-key",
-    "query": "06037",
-    "type": 7
-  }
-]New value: +[
+  {
+    "query": "90210",
+    "type": 1
+  },
+  {
+    "query": "06037",
+    "type": 7
+  }
+]

Changed1 schema field changedMay 8, 2026

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "properties": {
+    "crosswalk_type": {
+      "description": "Human-readable crosswalk type label",
+      "type": "string"
+    },
+    "data": {
+      "description": "Geographic crosswalk mapping data from HUD API",
+      "type": "object"
+    },
+    "query": {
+      "description": "Input query value provided in request",
+      "type": "string"
+    }
+  },
+  "required": [
+    "crosswalk_type",
+    "query",
+    "data"
+  ],
+  "type": "object"
+}

Changed1 schema field changedMay 6, 2026

addedInput schema / examples

Added value: +[
+  {
+    "_apiKey": "your-hud-api-key",
+    "query": "90210",
+    "type": 1
+  },
+  {
+    "_apiKey": "your-hud-api-key",
+    "query": "06037",
+    "type": 7
+  }
+]

First observedApr 22, 2026

TDQS

A4/5.0

Behavior3/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare readOnlyHint, idempotentHint, openWorldHint, and destructiveHint=false, so the safety profile is fully covered. The description adds only the return-value behavior ('Returns geographic identifiers') and does not contradict annotations. No rate-limit, auth, or data-vintage context is added, but with rich annotations the bar is lower; this is a standard, acceptable read-only tool description.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Three sentences, zero filler: the core action is front-loaded, the return value follows, and the use case is stated last. Every sentence earns its place for a tool with 3 params and full schema coverage.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness4/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a moderate-complexity tool with 3 fully documented params, an output schema, and strong safety annotations, the description plus schema give an agent everything needed to call it correctly. The only notable omission is data vintage/currentness (HUD crosswalk mappings change annually) and rate limits, which would be nice-to-have but are not required for correct invocation.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%: type codes (1=ZIP-to-tract, etc.), query format, and API key are all documented in the schema. The description reinforces the mapping directions for types 1-4 and hints at bidirectionality, adding marginal value but not compensating for anything—the schema already does the heavy lifting. Baseline 3 is appropriate.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb ('Map') plus resource ('ZIP codes to census tracts, counties, CBSAs, and congressional districts'), and names the return value ('geographic identifiers'). The description is immediately distinguishable from sibling HUD tools (income limits, fair market rents, CHAS), so an agent can disambiguate without inspecting schemas.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

'Use to translate between location code formats or join datasets' gives explicit, actionable context for when to invoke this tool. It does not name alternatives or state when not to use it, so it stops short of a 5, but the guidance is clear and unmissable.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

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