Census

Census Building Permits

census_building_permits

Read-onlyIdempotent

Check monthly building permits for new residential construction by geography. Returns count of authorized privately-owned housing units and construction 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	APERMITS (annual rate, default) or PERMITS (monthly level). Pass "ALL" to get every residential-construction series for the month.

Output Schema

Name	Required	Description
`date`	No
`note`	No
`time`	No	Time period queried
`count`	No
`units`	No
`results`	No	Array of monthly building permit records
`headline`	No
`category_code`	No

Schema Changelog

Changes observed during successful MCP inspections.

Changed10 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 / 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",
-  "results"
-]

Changed2 schema fields changedJul 26, 2026

changedInput schema / examples

Previous value: -[
-  {
-    "_apiKey": "your-census-api-key",
-    "time": "2024-01",
-    "variables": "PERMIT"
-  },
-  {
-    "_apiKey": "your-census-api-key",
-    "category_code": "TOTAL",
-    "time": "from+2023-01+to+2024-01",
-    "variables": "PERMIT,PERMIT_1UNIT"
-  }
-]New value: +[
+  {
+    "category_code": "APERMITS"
+  },
+  {
+    "category_code": "APERMITS",
+    "time": "2026-04"
+  }
+]

changedInput schema / properties / time / description

Previous 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."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."

Changed4 schema fields changedJul 26, 2026

changedInput schema / properties / category_code / description

Previous value: -"Category filter (e.g., \"TOTAL\" for total, \"1UNIT\" for single-family). Optional."New value: +"APERMITS (annual rate, default) or PERMITS (monthly level). Pass \"ALL\" to get every residential-construction series for the month."

changedInput schema / properties / time / description

Previous value: -"Time period (e.g., \"2024-01\" for January 2024, \"from+2023-01+to+2024-01\" for a range)."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."

removedInput schema / properties / variables

Removed value: -{
-  "description": "Comma-separated variables (e.g., \"PERMIT\" for total permits, \"PERMIT_1UNIT\" for single-family). Use census_available_datasets to discover variables.",
-  "type": "string"
-}

removedInput schema / required

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

Changed1 schema field changedMay 8, 2026

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "properties": {
+    "results": {
+      "description": "Array of monthly building permit records",
+      "items": {
+        "additionalProperties": {
+          "type": "string"
+        },
+        "description": "Building permits 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",
+    "results"
+  ],
+  "type": "object"
+}

Changed1 schema field changedMay 6, 2026

addedInput schema / examples

Added value: +[
+  {
+    "_apiKey": "your-census-api-key",
+    "time": "2024-01",
+    "variables": "PERMIT"
+  },
+  {
+    "_apiKey": "your-census-api-key",
+    "category_code": "TOTAL",
+    "time": "from+2023-01+to+2024-01",
+    "variables": "PERMIT,PERMIT_1UNIT"
+  }
+]

First observedApr 22, 2026

TDQS

A3.7/5.0

Behavior3/5

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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint. The description adds that it returns counts and trends, which is minimally extra beyond annotations and the output schema.

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, front-loaded with the action, no extraneous content. Every word earns its place.

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

Completeness3/5

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

The description mentions 'by geography' but the input schema lacks a geography parameter, creating ambiguity. Output schema and annotations cover other aspects, so overall moderately complete.

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 schema already explains each parameter. The description does not add further parameter meaning, which is acceptable given full schema coverage.

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 checks monthly building permits for new residential construction by geography, and returns specific data. It distinguishes itself from sibling census tools like census_housing_starts.

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 usage for building permit data but does not explicitly state when to use this tool versus alternatives like census_housing_starts or census_acs. No when-not guidance is provided.

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

All Census tools Inspect

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