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union

Perform a union operation on two geometries to merge them into a single geometry. Input two geometry strings and receive the combined result for spatial analysis.

Instructions

Combine two geometries.

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": {
      "geometry1": "<geometry1>",
      "geometry2": "<geometry2>"
    },
    "name": "union"
  }
}

Input Schema

Name	Required	Description	Default
`geometry1`	Yes
`geometry2`	Yes

Output Schema

Name	Required	Description	Default
No arguments

Schema Changelog

Changes observed during successful MCP inspections.

Changed4 schema fields changedv1.0.0Jan 2, 2026
- removedInput schema / properties / geometry1 / title
```
Removed value: -"Geometry1"
```
- removedInput schema / properties / geometry2 / title
```
Removed value: -"Geometry2"
```
- removedInput schema / title
```
Removed value: -"unionArguments"
```
- changedOutput schema / (root)
```
Previous value: -nullNew value: +{
+  "additionalProperties": true,
+  "type": "object"
+}
```
First observedAug 19, 2025

TDQS

D1.9/5.0

Behavior1/5

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

With no annotations, the description bears full burden but only states 'combine two geometries.' No disclosure of output type, error handling, or side effects. Output schema exists but description adds no behavioral context.

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

Conciseness2/5

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

Extremely concise (3 words) but lacks structure and essential details. Conciseness is not matched by informativeness; it sacrifices completeness.

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

Completeness1/5

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

Given zero annotations and no parameter descriptions, the description is insufficient. Even with an output schema, the description fails to explain behavior, prerequisites, or output semantics.

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

Parameters1/5

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

Schema coverage is 0% and description does not describe parameters. No explanation of expected format (WKT, GeoJSON) or constraints for geometry1 and geometry2.

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

Purpose4/5

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

Description 'Combine two geometries' states action and resource clearly, aligning with tool name 'union.' It distinguishes from unary operations like unary_union_geometries but does not differentiate from other binary set operations like intersection or symmetric_difference.

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

Usage Guidelines1/5

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

No guidance on when to use this tool versus alternatives such as intersection, difference, or symmetric_difference. No context on prerequisites or 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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