generate_npc

THE RISK

Medium Risk

Why generate_npc needs a policy

The tool creates new data (NPC records with stats and backgrounds) within the game world, which is a reversible write operation. This is not a Read operation (no retrieval without side effects), not Execute (no arbitrary code execution or external operations), not Destructive (NPCs can be deleted), and not Financial.

From the tool's definition Tool is named 'generate_npc' and explicitly described as 'Generate a random NPC with stats and background.' This creates new game content (NPC characters with attributes) in the FoundryVTT world.

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

POLICY

How to control generate_npc

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

policy.json

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

generate_npc 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 FoundryVTT 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 FoundryVTT MCP Server tools

Destructive delete_actor_item Delete an item owned by an actor (requires FOUNDRY_WRITE_ENABLED + active Socket.IO connec Execute roll_dice Roll dice using standard RPG notation (e.g., 1d20, 3d6+4) Write create_actor_item Create an item on an actor from an inline item document (requires FOUNDRY_WRITE_ENABLED + Write generate_loot Generate random loot for encounters Write update_actor_attributes Update attributes on an actor Read diagnose_errors Stub: returns raw logs without analysis. Full diagnostic logic is tracked in 133 and not y Read get_actor_details Get detailed information about a specific actor Read get_chat_messages Get recent chat messages from the game

All 25 FoundryVTT MCP Server tools →

Write tools on other servers

M-Team MCP Server download_torrent YouTube MCP Server generate_video_title Android Forensics ADB MCP Server combine_reports 0xarchive web3_signup

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 generate_npc

What does the generate_npc tool do? +

Generate a random NPC with stats and background. It is categorised as a Write tool in the FoundryVTT 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 generate_npc? +

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

What risk level is generate_npc? +

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

Can I rate-limit generate_npc? +

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

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

generate_npc is provided by the FoundryVTT MCP Server MCP server (laurigates/foundryvtt-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every FoundryVTT MCP Server tool call.

Start from FoundryVTT 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 →