AI agents use modify_timer 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.
This tool performs a Write operation: it modifies (updates) a game timer, which is a normal part of game state management in an RPG system. Timers can be adjusted, reset, or extended without permanent loss of data. While it affects game progression, the effect is limited to the local game session and is fully reversible through another modification.
From the tool's definition Tool modifies a timer within the game state—a reversible change to game data. The description states 'Modify a timer,' which indicates creating or altering existing game state without deletion or irreversible harm.
Documented attack patterns abuse exactly the kind of access modify_timer 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_timer:
{
"version": "1",
"default": "deny",
"tools": {
"modify_timer": {
"limits": [
{
"counter": "modify_timer_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}modify_timer 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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Modify a timer. 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_timer: 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_timer 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_timer 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_timer. 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_timer 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.
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