AI agents invoke contest to trigger actions in DMCP. What it does depends on the arguments the agent supplies, and its effects often reach beyond the immediate call — builds kicked off, notifications sent, workflows started.
The tool triggers a game mechanic (an opposed check/contest) between two characters, which constitutes executing a game operation that calculates outcomes based on arguments. It has no real-world side effects beyond modifying game state, making it low severity.
From the tool's definition Opposed check between two characters
Documented attack patterns abuse exactly the kind of access contest 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 contest:
{
"version": "1",
"default": "deny",
"tools": {
"contest": {
"limits": [
{
"counter": "contest_rate",
"window": "minute",
"max": 10,
"scope": "grant"
}
]
}
}
}contest stays usable, but rate-capped — a runaway agent can't fire it dozens of times a minute. Everything else on the server is denied unless you say otherwise.
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Opposed check between two characters. It is categorised as a Execute tool in the DMCP MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.
Register the D MCP server in PolicyLayer and add a rule for contest: 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.
contest is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.
Yes. Add a rate_limit block to the contest 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 contest. 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.
contest 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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