apply_effect · DM20 Protocol MCP: Risk & Policy

WHAT IT DOES

What apply_effect does on DM20 Protocol

AI agents use apply_effect to create or update resources in DM20 Protocol — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your DM20 Protocol environment.

WHY IT NEEDS A POLICY

Why apply_effect needs a policy

In a D&D campaign context, applying effects (buffs, debuffs, conditions) modifies character state reversibly. This is a Write operation—data is created or changed but not permanently destroyed. Severity is medium because misuse could disrupt game balance or character integrity, but effects can generally be undone.

From the tool's definition Tool name 'apply_effect' suggests modifying game state. Based on sibling tools like 'add_death_save', 'add_spell', and 'add_item_to_character', this server modifies character sheets and campaign state.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

apply_effect Rate-limited

apply_effect 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": {
    "apply_effect": {
      "limits": [
        {
          "counter": "apply_effect_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 DM20 Protocol, so you can run agents against it safely.

FAQ

Questions about apply_effect

What does the apply_effect tool do? +

apply_effect. It is categorised as a Write tool in the DM20 Protocol MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on apply_effect? +

Register the DM20 Protocol MCP server in PolicyLayer and add a rule for apply_effect: 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 DM20 Protocol. Nothing to install.

What risk level is apply_effect? +

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

Can I rate-limit apply_effect? +

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

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

apply_effect is provided by the DM20 Protocol MCP server (polloinfilzato/dm20-protocol). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.