QGIS MCP Server

Set Layer CRS

set_layer_crs

Change how a layer's coordinates are interpreted by assigning a CRS such as 'EPSG:4326'. Sets the CRS without reprojecting the data.

Instructions

Set the CRS of a layer (e.g. 'EPSG:4326'). This does NOT reproject data - it only changes how the layer's coordinates are interpreted.

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": {
      "layer_id": "<layer_id>",
      "crs": "<crs>"
    },
    "name": "set_layer_crs"
  }
}

Input Schema

Name	Required	Description	Default
`crs`	Yes
`layer_id`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.1.0Nov 13, 2026

TDQS

A4.3/5.0

Behavior4/5

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

With no annotations provided, the description carries the transparency burden. It discloses a critical non-obvious behavior: changing CRS interpretation without reprojecting coordinates. It does not mention other side effects, but this is the key behavioral trait for this operation.

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 with no filler. The first sentence states the purpose, the second immediately clarifies a critical caveat. Ideal conciseness and structure.

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?

For a simple two-parameter tool with no output schema, the description is complete. It covers the action, the format example, and the important caveat about not reprojecting. No further context is needed.

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 0%, so the description must compensate. It adds an example for the 'crs' parameter ('EPSG:4326'), which helps clarify expected format, but does not describe the 'layer_id' parameter beyond its name. The schema's string type is minimal, and the description adds only marginal 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 the action: 'Set the CRS of a layer' with an explicit example format. It distinguishes itself from sibling tools like get_layer_crs (which retrieves) and set_project_crs (which operates on the project).

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?

The description provides a clear 'when not to use' by stating 'This does NOT reproject data', which helps agents avoid misuse. However, it does not name an alternative tool (e.g., transform_coordinates) for reprojection, so it stops short of full alternatives guidance.

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

Deploy Server