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QGIS MCP

QGIS MCP

by lefcgis
OverviewSchemaSourceRelated ServersDiscussionsAdmin
Python
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Sample Raster Values

sample_raster_values
Read-only

Sample pixel values from a raster layer at given point coordinates. Optionally specify a band; otherwise all bands are sampled.

Instructions

Sample raster pixel values at points. 'points' is a list of [x, y] in the raster's CRS. Omit 'band' to sample all bands. Use transform_coordinates first if your points are in a different CRS.

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": {
      "raster_layer": "<raster_layer>",
      "points": "<points>"
    },
    "name": "sample_raster_values"
  }
}

Input Schema

NameRequiredDescriptionDefault
bandNo
pointsYes
raster_layerYes

Output Schema

NameRequiredDescriptionDefault

No arguments

Schema Changelog

Changes observed during successful MCP inspections.

  1. First observedv0.5.0

TDQS

A4.6/5.0
Behavior4/5

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

Annotations already declare readOnlyHint=true, so no contradiction. Description adds context about CRS requirements and sampling all bands, which complements the annotation. Could mention performance for many points, but not required.

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, each packed with essential information: what the tool does, parameter details, and a usage prerequisite. No wasted words.

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?

Covers the main behavioral aspects: CRS requirement, band behavior. With an output schema present, not explaining return values is fine. Missing details like error handling or limits, but acceptable for the complexity level.

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 0%, so description must compensate. It does for 'points' (explains format and CRS) and 'band' (explains default behavior). 'raster_layer' is self-evident from the name, so overall adds sufficient meaning.

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 'Sample raster pixel values at points', which is a specific verb (sample) and resource (raster values at points). This distinguishes it from siblings like zonal_statistics (polygon-based) and get_raster_info (metadata).

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?

Explicitly tells when to use an alternative: 'Use transform_coordinates first if your points are in a different CRS.' Also advises on band usage: 'Omit 'band' to sample all bands.' This provides clear context for tool selection.

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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