unary_union_geometries

THE RISK

Medium Risk

Why unary_union_geometries needs a policy

The tool performs a geometric computation that combines input geometries into a new unified geometry. This is reversible (the original geometries are not destroyed, and the operation can be re-run or undone) and does not execute arbitrary code or delete data. It fits the Write category as it creates/transforms geospatial data.

From the tool's definition Tool creates a union of multiple geometries, which modifies/combines geometric data. Description explicitly states 'Create a union', indicating data transformation.

Documented attack patterns abuse exactly the kind of access unary_union_geometries gives an agent:

POLICY

How to control unary_union_geometries

PolicyLayer is an MCP gateway — it sits between your AI agents and GIS MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for unary_union_geometries:

policy.json

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

unary_union_geometries 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.

Create a free account and register GIS MCP Server — nothing to install.
Add this policy — paste it, or build it visually.
Point your MCP client (Claude, Cursor, anything) at your gateway URL.

LIMIT THIS TOOL →

Free to start. No card required.

EXPLORE

Related tools and policies

More GIS MCP Server tools

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All 98 GIS MCP Server tools →

Write tools on other servers

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Go deeper

The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Argument validation → Checking tool call arguments against schema and policy before they run.
Scoped token → Per-person credentials that grant a defined subset of servers and tools.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →

FAQ

Questions about unary_union_geometries

What does the unary_union_geometries tool do? +

Create a union of multiple geometries. It is categorised as a Write tool in the GIS MCP Server MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on unary_union_geometries? +

Register the GIS MCP Server MCP server in PolicyLayer and add a rule for unary_union_geometries: 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 GIS MCP Server. Nothing to install.

What risk level is unary_union_geometries? +

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

Can I rate-limit unary_union_geometries? +

Yes. Add a rate_limit block to the unary_union_geometries 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 unary_union_geometries completely? +

Set action: deny in the PolicyLayer policy for unary_union_geometries. 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 unary_union_geometries? +

unary_union_geometries is provided by the GIS MCP Server MCP server (mahdin75/gis-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every GIS MCP Server tool call.

Start from GIS MCP Server, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.

CHECK YOUR STACK →