fl_add_field · ArcGIS MCP: Risk & Policy

WHAT IT DOES

What fl_add_field does on ArcGIS MCP

AI agents use fl_add_field 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 fl_add_field needs a policy

The tool creates a new field (column) in a feature layer, which is a reversible write operation that modifies data schema. This matches the Write category (creates/modifies data reversibly). Severity is medium because inadvertently adding fields to production feature layers could disrupt dependent applications or data structures, though the change is reversible via field deletion.

From the tool's definition Tool name 'fl_add_field' indicates field addition to a feature layer; located on ArcGIS MCP server alongside feature layer editing tools per server description.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

fl_add_field Rate-limited

fl_add_field 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": {
    "fl_add_field": {
      "limits": [
        {
          "counter": "fl_add_field_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 fl_add_field

What does the fl_add_field tool do? +

fl_add_field. 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 fl_add_field? +

Register the ArcGIS MCP server in PolicyLayer and add a rule for fl_add_field: 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 fl_add_field? +

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

Can I rate-limit fl_add_field? +

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

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

fl_add_field 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.