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geo_area

Area in square metres enclosed by a ring of 3+ coordinates, computed geodesically. Always positive: the answer does not depend on whether the ring is wound clockwise or anticlockwise. Intended for zones and boundaries, not for polygons covering more than half the globe. Local computation: no network call, no quota.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
pointsYesThe coordinates to consider.

Output Schema

TableJSON Schema
NameRequiredDescriptionDefault
area_sq_mYesEnclosed area in square metres, always positive regardless of winding order.

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed5 schema fields changed
    • addedInput schema / $defs / LatLon / anyOf
      Added value: +[
+  {
+    "properties": {
+      "lat": {
+        "description": "Latitude in decimal degrees (−90 to 90).",
+        "format": "double",
+        "type": "number"
+      },
+      "lon": {
+        "description": "Longitude in decimal degrees (−180 to 180).",
+        "format": "double",
+        "type": "number"
+      }
+    },
+    "required": [
+      "lat",
+      "lon"
+    ],
+    "type": "object"
+  },
+  {
+    "description": "GeoJSON position [lon, lat]: longitude FIRST.",
+    "items": {
+      "format": "double",
+      "type": "number"
+    },
+    "maxItems": 2,
+    "minItems": 2,
+    "type": "array"
+  }
+]
    • changedInput schema / $defs / LatLon / description
      Previous value: -"A WGS84 coordinate pair in decimal degrees."New value: +"A WGS84 coordinate in decimal degrees: a {lat, lon} object (preferred), or a GeoJSON [lon, lat] array with LONGITUDE FIRST, the same order as every polygon field on this server."
    • removedInput schema / $defs / LatLon / properties
      Removed value: -{
-  "lat": {
-    "description": "Latitude in decimal degrees (−90 to 90).",
-    "format": "double",
-    "type": "number"
-  },
-  "lon": {
-    "description": "Longitude in decimal degrees (−180 to 180).",
-    "format": "double",
-    "type": "number"
-  }
-}
    • removedInput schema / $defs / LatLon / required
      Removed value: -[
-  "lat",
-  "lon"
-]
    • removedInput schema / $defs / LatLon / type
      Removed value: -"object"
  2. First observed

TDQS

A4.6/5.0
Behavior4/5

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

With no annotations provided, the description carries the full burden of behavioral disclosure. It discloses that the result is always positive regardless of winding order, that computation is geodesic, and that it is local with no quota. It does not mention edge cases like degenerate rings or the exact return format, but the output schema likely covers the return value. The description adds meaningful behavioral context beyond the 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?

The description is four sentences, each earning its place: what it computes, the winding-order invariance, the intended scope, and the local-computation note. It is front-loaded with the core purpose and avoids redundancy with the schema.

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 single-parameter tool with a rich schema and an output schema, the description is nearly complete. It covers the main behavioral traits and usage constraints. The only minor gap is not stating what happens with fewer than 3 points or degenerate rings, but the description already says '3+ coordinates' and the schema requires an array, so this is adequately implied.

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

Parameters4/5

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

Schema description coverage is 100%, so the schema already documents the 'points' parameter and the LatLon format. The description adds the key semantic constraint that the ring must have 3+ coordinates and that the area is computed geodesically, which is not fully explicit in the schema. This compensates for the schema's generic 'coordinates to consider' phrasing.

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 states a specific verb ('Area in square metres enclosed by a ring of 3+ coordinates') and a clear resource, distinguishing it from sibling geo tools like geo_distance, geo_length, and geo_centroid. It also clarifies the geodesic computation and the intended use case, so an agent can tell it apart from other geometry tools without opening the schema.

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

Usage Guidelines5/5

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

The description explicitly says when to use it ('Intended for zones and boundaries') and when not to ('not for polygons covering more than half the globe'). It also notes the local computation ('no network call, no quota'), which helps an agent choose it over network-dependent alternatives. This is clear usage guidance with exclusions.

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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