webmap_add_layer · ArcGIS MCP: Risk & Policy

WHAT IT DOES

What webmap_add_layer does on ArcGIS MCP

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

WHY IT NEEDS A POLICY

Why webmap_add_layer needs a policy

The tool adds a layer to a webmap, which is a reversible modification of a data structure. This falls under Write rather than Execute because it modifies a specific artifact rather than executing arbitrary code. However, confidence is moderate (0.72) because the description is empty, preventing verification of side effects or scope.

From the tool's definition Tool name 'webmap_add_layer' indicates it adds (creates/modifies) a layer within a webmap artifact. The 'add' verb and 'layer' object imply write-class functionality that creates or modifies the webmap structure.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

webmap_add_layer Rate-limited

webmap_add_layer 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": {
    "webmap_add_layer": {
      "limits": [
        {
          "counter": "webmap_add_layer_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 ArcGIS MCP, so you can run agents against it safely.

FAQ

Questions about webmap_add_layer

What does the webmap_add_layer tool do? +

webmap_add_layer. It is categorised as a Write tool in the ArcGIS 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 webmap_add_layer? +

Register the ArcGIS MCP server in PolicyLayer and add a rule for webmap_add_layer: 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 ArcGIS MCP. Nothing to install.

What risk level is webmap_add_layer? +

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

Can I rate-limit webmap_add_layer? +

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

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

webmap_add_layer is provided by the ArcGIS MCP server (renemorenow/arcgis-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.