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TypeScript

Hybrid

Union Polygons

union_tool

Read-onlyIdempotent

Merge multiple polygons into one geometry to combine service areas or coverage regions. Operates offline without API calls.

Instructions

Merge two or more polygons into a single unified geometry. Useful for combining service areas, delivery zones, isochrones, or coverage regions. Returns a Polygon or MultiPolygon if the inputs do not overlap. Works offline without API calls.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "polygons": "<polygons>"
    },
    "name": "union_tool"
  }
}

Input Schema

Name	Required	Description	Default
`polygons`	Yes	Array of polygons to merge into a single union geometry

Output Schema

Name	Required	Description	Default
`type`	Yes	Geometry type: Polygon or MultiPolygon
`geometry`	Yes	GeoJSON geometry of the merged polygon (Polygon or MultiPolygon)

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.12.6Jul 15, 2026

TDQS

A4.3/5.0

Behavior4/5

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

Discloses behavior beyond annotations: returns Polygon or MultiPolygon if inputs do not overlap, works offline without API calls. Annotations already mark readOnlyHint, idempotentHint, destructiveHint, so description adds useful context.

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, each serving a purpose: purpose, use cases, behavioral note. No fluff.

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

Completeness5/5

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

With rich annotations and full schema coverage, the description provides complete context: purpose, usage, behavioral trait, and offline capability. Output schema exists, so return value details are covered.

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 coverage is 100%; the description repeats that polygons are merged but adds no new details about the parameter itself. 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?

Clear verb ('Merge') and resource ('polygons'). Mentions specific use cases like combining service areas, delivery zones, isochrones, coverage regions. Distinguishes from sibling tools like difference_tool and intersect_tool.

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?

Provides context on when to use (e.g., combining coverage regions) and notes offline capability. Does not explicitly say when not to use or list alternatives.

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