run_command · Shell MCP: Risk & Policy

WHAT IT DOES

What run_command does on Shell

AI agents invoke run_command to trigger actions in Shell. 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 run_command needs a policy

This tool executes shell commands, making it Execute category. While the description mentions 'safely' and the server advertises 'security layers including command whitelisting and directory restrictions,' these are mitigations rather than functional limiters—the tool's core capability is arbitrary code execution.

From the tool's definition Tool name 'run_command' and description 'Run a shell command safely' explicitly indicates execution of shell commands, which is the definition of Execute category.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

run_command Rate-limited

run_command 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": {
    "run_command": {
      "limits": [
        {
          "counter": "run_command_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 Shell, so you can run agents against it safely.

FAQ

Questions about run_command

What does the run_command tool do? +

Run a shell command safely. It is categorised as a Execute tool in the Shell MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on run_command? +

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

What risk level is run_command? +

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

Can I rate-limit run_command? +

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

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

run_command is provided by the Shell MCP server (kg912/shell-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.