AI agents use create_npc to create or update resources in D&D MCP Server — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your D&D MCP Server environment.
This tool creates new data (NPC records) that can be modified or deleted later, making it a Write operation rather than Read, Execute, Destructive, Financial, or Other. Severity is medium because creating NPCs is reversible and has limited scope—an agent could pollute campaign data with unwanted NPCs, but this doesn't cause financial harm, execute arbitrary code, or irreversibly destroy data.
From the tool's definition Tool name 'create_npc' indicates creation of a new NPC (non-player character) entity in a D&D campaign management system.
Documented attack patterns abuse exactly the kind of access create_npc gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and D&D MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for create_npc:
{
"version": "1",
"default": "deny",
"tools": {
"create_npc": {
"limits": [
{
"counter": "create_npc_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}create_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.
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create_npc. It is categorised as a Write tool in the D&D MCP Server MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the D&D MCP Server MCP server in PolicyLayer and add a rule for create_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 D&D MCP Server. Nothing to install.
create_npc is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.
Yes. Add a rate_limit block to the create_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.
Set action: deny in the PolicyLayer policy for create_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.
create_npc is provided by the D&D MCP Server MCP server (study-flamingo/gamemaster-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from D&D MCP Server, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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30 D&D MCP Server tools catalogued and risk-classified — across an index of 43,000+ MCP servers.