Add or remove stacks from a status effect
AI agents use modify_effect_stacks to create or update resources in DMCP — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your DMCP environment.
The tool modifies game state (status effect stacks) in a way that can be undone or reversed by adding/removing stacks in the opposite direction. This is characteristic of Write operations (reversible updates) rather than Destructive (irreversible deletion).
From the tool's definition Tool description states 'Add or remove stacks from a status effect' — these are reversible modifications to game state data. The word 'Add' and 'remove' indicate creation and deletion of stacks, not irreversible destruction of the entire effect or character.
Documented attack patterns abuse exactly the kind of access modify_effect_stacks gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and DMCP, and nothing reaches the server without passing your rules. This is the rule we recommend for modify_effect_stacks:
{
"version": "1",
"default": "deny",
"tools": {
"modify_effect_stacks": {
"limits": [
{
"counter": "modify_effect_stacks_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}modify_effect_stacks 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.
Free to start. No card required.
Add or remove stacks from a status effect. It is categorised as a Write tool in the DMCP MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the D MCP server in PolicyLayer and add a rule for modify_effect_stacks: 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 DMCP. Nothing to install.
modify_effect_stacks 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 modify_effect_stacks 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 modify_effect_stacks. 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.
modify_effect_stacks is provided by the D MCP server (shawnrushefsky/dmcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from DMCP, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
Free to start. No card required.
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