set_canvas_scale · QGIS MCP: Risk & Policy

WHAT IT DOES

What set_canvas_scale does on QGIS MCP

AI agents use set_canvas_scale to create or update resources in QGIS MCP — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your QGIS MCP environment.

WHY IT NEEDS A POLICY

Why set_canvas_scale needs a policy

This tool modifies the visualization state of the QGIS canvas by changing scale and rotation settings. These are reversible changes (can be undone or reset), affecting the display layer rather than data itself. This qualifies as Write rather than Execute because it adjusts configuration/state without executing arbitrary operations.

From the tool's definition Tool name 'set_canvas_scale' with description 'Set the map canvas scale and/or rotation' indicates modification of canvas state (scale and rotation parameters).

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

set_canvas_scale Rate-limited

set_canvas_scale stays usable, but capped — an agent stuck in a loop can't make hundreds of changes a minute. Everything else on the server is denied unless you say otherwise.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "set_canvas_scale": {
      "limits": [
        {
          "counter": "set_canvas_scale_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

LIMIT THIS TOOL →

Instant setup, no code required.

PolicyLayer is an MCP gateway: every tool call is checked against your rule before it reaches QGIS MCP, so you can run agents against it safely.

FAQ

Questions about set_canvas_scale

What does the set_canvas_scale tool do? +

Set the map canvas scale and/or rotation. Provide scale as denominator. It is categorised as a Write tool in the QGIS MCP MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on set_canvas_scale? +

Register the QGIS MCP server in PolicyLayer and add a rule for set_canvas_scale: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches QGIS MCP. Nothing to install.

What risk level is set_canvas_scale? +

set_canvas_scale is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.

Can I rate-limit set_canvas_scale? +

Yes. Add a rate_limit block to the set_canvas_scale rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.

How do I block set_canvas_scale completely? +

Set action: deny in the PolicyLayer policy for set_canvas_scale. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.

What MCP server provides set_canvas_scale? +

set_canvas_scale is provided by the QGIS MCP server (nkarasiak/qgis-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.