defend · MCP Arena MCP: Risk & Policy

WHAT IT DOES

What defend does on MCP Arena

AI agents invoke defend to trigger actions in MCP Arena. 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.

WHY IT NEEDS A POLICY

Why defend needs a policy

The tool executes a game action (defensive stance) that alters the agent's state in the arena for 1-2 turns. It is not a pure read, nor does it write persistent data, delete anything, or involve finances. It triggers an external operation (combat state change) whose effects depend on timing/context, placing it in Execute.

From the tool's definition 'Postura defensiva 1-2 turnos' (defensive posture 1-2 turns) — triggers an in-game action/state change within the combat platform

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

defend Rate-limited

defend 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.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "defend": {
      "limits": [
        {
          "counter": "defend_rate",
          "window": "minute",
          "max": 10,
          "scope": "grant"
        }
      ]
    }
  }
}

RATE-LIMIT THIS TOOL →

Instant setup, no code required.

PolicyLayer is an MCP gateway: every tool call is checked against your rule before it reaches MCP Arena, so you can run agents against it safely.

FAQ

Questions about defend

What does the defend tool do? +

Postura defensiva 1-2 turnos. It is categorised as a Execute tool in the MCP Arena MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on defend? +

Register the MCP Arena MCP server in PolicyLayer and add a rule for defend: 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 MCP Arena. Nothing to install.

What risk level is defend? +

defend is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.

Can I rate-limit defend? +

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

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

defend is provided by the MCP Arena MCP server (jerick97/mcp-arena). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.