AI agents invoke vm_stop to trigger actions in tmux-claude MCP Server. 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.
This tool executes a command to stop a VM instance, which is a significant external operation that affects system state. While not permanently destructive (VMs can be restarted), it disrupts service availability and has material operational consequences. It falls under Execute rather than Destructive because stopping is reversible via restart.
From the tool's definition Tool name 'vm_stop' and description 'Stop a running VM instance' indicate an action that halts a running system process/service. Stopping a VM is an external operation whose effects depend on which VM is targeted.
Documented attack patterns abuse exactly the kind of access vm_stop gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and tmux-claude MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for vm_stop:
{
"version": "1",
"default": "deny",
"tools": {
"vm_stop": {
"limits": [
{
"counter": "vm_stop_rate",
"window": "minute",
"max": 10,
"scope": "grant"
}
]
}
}
}vm_stop 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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Stop a running VM instance. It is categorised as a Execute tool in the tmux-claude MCP Server MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.
Register the tmux-claude MCP Server MCP server in PolicyLayer and add a rule for vm_stop: 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 tmux-claude MCP Server. Nothing to install.
vm_stop 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 vm_stop 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 vm_stop. 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.
vm_stop is provided by the tmux-claude MCP Server MCP server (michael-abdo/tmux-claude-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from tmux-claude MCP Server, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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26 tmux-claude MCP Server tools catalogued and risk-classified — across an index of 43,000+ MCP servers.