Census

Census Housing Starts

census_housing_starts

Read-onlyIdempotent

Get residential construction pipeline by geography: new starts, units under construction, and completed units. Returns housing supply and activity trends.

Input Schema

Name	Required	Description
`time`	No	Month as "YYYY-MM" (e.g. "2026-04"), or "from 2026-01 to 2026-04" for a range. Defaults to the latest published month.
`_apiKey`	No	Census API key
`category_code`	No	ASTARTS (annual rate, default), STARTS, COMPLETIONS, UNDERCONST, AUTHNOTSTD, or "ALL".

Output Schema

Name	Required	Description
`date`	No
`note`	No
`time`	No	Time period queried
`count`	No
`units`	No
`results`	No	Array of housing starts records
`headline`	No
`category_code`	No

Schema Changelog

Changes observed during successful MCP inspections.

Changed11 schema fields changedJul 28, 2026

addedOutput schema / properties / category_code
```
Added value: +{
+  "type": "string"
+}
```
addedOutput schema / properties / count
```
Added value: +{
+  "type": "number"
+}
```
addedOutput schema / properties / date
```
Added value: +{
+  "type": "string"
+}
```

addedOutput schema / properties / headline

Added value: +{
+  "properties": {
+    "category_code": {
+      "type": "string"
+    },
+    "geography": {
+      "type": "string"
+    },
+    "period": {
+      "type": "string"
+    },
+    "units": {
+      "type": "string"
+    },
+    "value_thousands": {
+      "type": "number"
+    }
+  },
+  "type": "object"
+}

addedOutput schema / properties / note
```
Added value: +{
+  "type": "string"
+}
```

removedOutput schema / properties / region

Removed value: -{
-  "description": "Census region or 'all' if none specified",
-  "type": "string"
-}

removedOutput schema / properties / results / items / additionalProperties
```
Removed value: -{
-  "type": "string"
-}
```

addedOutput schema / properties / results / items / properties

Added value: +{
+  "category_code": {
+    "type": "string"
+  },
+  "cell_value": {
+    "type": "string"
+  },
+  "data_type_code": {
+    "type": "string"
+  },
+  "geo_level_code": {
+    "type": "string"
+  },
+  "seasonally_adj": {
+    "type": "string"
+  },
+  "time": {
+    "type": "string"
+  },
+  "time_slot_id": {
+    "type": "string"
+  },
+  "time_slot_name": {
+    "type": "string"
+  }
+}

addedOutput schema / properties / units
```
Added value: +{
+  "type": "string"
+}
```

removedOutput schema / properties / variables

Removed value: -{
-  "description": "Variable codes requested",
-  "items": {
-    "type": "string"
-  },
-  "type": "array"
-}

removedOutput schema / required

Removed value: -[
-  "variables",
-  "time",
-  "region",
-  "results"
-]

Changed2 schema fields changedJul 26, 2026

changedInput schema / examples

Previous value: -[
-  {
-    "_apiKey": "your-census-api-key",
-    "time": "2024-01",
-    "variables": "STARTS"
-  },
-  {
-    "_apiKey": "your-census-api-key",
-    "region": "W",
-    "time": "2024-01",
-    "variables": "STARTS,UNDER_CONSTRUCTION,COMPLETIONS"
-  }
-]New value: +[
+  {
+    "category_code": "ASTARTS"
+  },
+  {
+    "category_code": "ASTARTS",
+    "time": "2026-04"
+  }
+]

changedInput schema / properties / time / description

Previous value: -"Month as \"YYYY-MM\" (e.g. \"2026-04\"). Defaults to the latest published month."New value: +"Month as \"YYYY-MM\" (e.g. \"2026-04\"), or \"from 2026-01 to 2026-04\" for a range. Defaults to the latest published month."

Changed5 schema fields changedJul 26, 2026

addedInput schema / properties / category_code

Added value: +{
+  "description": "ASTARTS (annual rate, default), STARTS, COMPLETIONS, UNDERCONST, AUTHNOTSTD, or \"ALL\".",
+  "type": "string"
+}

removedInput schema / properties / region

Removed value: -{
-  "description": "Census region filter (e.g., \"NE\" for Northeast, \"MW\" for Midwest, \"S\" for South, \"W\" for West). Optional.",
-  "type": "string"
-}

changedInput schema / properties / time / description

Previous value: -"Time period (e.g., \"2024-01\" for January 2024)."New value: +"Month as \"YYYY-MM\" (e.g. \"2026-04\"). Defaults to the latest published month."

removedInput schema / properties / variables

Removed value: -{
-  "description": "Comma-separated variables (e.g., \"STARTS\" for housing starts, \"UNDER_CONSTRUCTION\", \"COMPLETIONS\").",
-  "type": "string"
-}

removedInput schema / required

Removed value: -[
-  "variables",
-  "time",
-  "_apiKey"
-]

Changed1 schema field changedMay 8, 2026

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "properties": {
+    "region": {
+      "description": "Census region or 'all' if none specified",
+      "type": "string"
+    },
+    "results": {
+      "description": "Array of housing starts records",
+      "items": {
+        "additionalProperties": {
+          "type": "string"
+        },
+        "description": "Housing starts data rows",
+        "type": "object"
+      },
+      "type": "array"
+    },
+    "time": {
+      "description": "Time period queried",
+      "type": "string"
+    },
+    "variables": {
+      "description": "Variable codes requested",
+      "items": {
+        "type": "string"
+      },
+      "type": "array"
+    }
+  },
+  "required": [
+    "variables",
+    "time",
+    "region",
+    "results"
+  ],
+  "type": "object"
+}

Changed1 schema field changedMay 6, 2026

addedInput schema / examples

Added value: +[
+  {
+    "_apiKey": "your-census-api-key",
+    "time": "2024-01",
+    "variables": "STARTS"
+  },
+  {
+    "_apiKey": "your-census-api-key",
+    "region": "W",
+    "time": "2024-01",
+    "variables": "STARTS,UNDER_CONSTRUCTION,COMPLETIONS"
+  }
+]

First observedApr 22, 2026

TDQS

A4/5.0

Behavior4/5

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

The description adds behavioral context beyond annotations by specifying the returned data types (new starts, units under construction, completed units) and stating it returns housing supply and activity trends. Annotations already indicate read-only, idempotent, non-destructive behavior.

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?

Two sentences efficiently convey the tool's purpose and output. Every word adds value, with no unnecessary details. The information is front-loaded in the first sentence.

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?

Given the presence of an output schema (not shown but confirmed) and rich annotations, the description sufficiently explains the tool's function and return types. It could be strengthened by mentioning the default geographic scope or lack thereof.

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%, so the description does not need to add much. It mentions 'by geography' (not in schema) and enumerates data types that map to category_code, but these are already covered by the schema. No significant new parameter semantics added.

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?

The description clearly states the tool retrieves residential construction pipeline data by geography, including starts, under construction, and completed units. It distinguishes from sibling tools like census_building_permits and census_homeownership by its focus on housing starts and pipeline metrics.

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

Usage Guidelines3/5

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

The description implies use when needing housing construction pipeline data, but it does not explicitly state when to use this tool over alternatives, nor does it provide context for exclusions or prerequisites.

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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