tmux_send_keys · Tmux MCP Server MCP: Risk & Policy

WHAT IT DOES

What tmux_send_keys does on Tmux MCP Server

AI agents invoke tmux_send_keys to trigger actions in Tmux 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.

WHY IT NEEDS A POLICY

Why tmux_send_keys needs a policy

tmux_send_keys effectively executes arbitrary shell commands in a live terminal session. Any command—including destructive, financial, or system-altering ones—can be run. The blast radius is critical because an AI agent could send any shell command (rm -rf, curl to exfiltrate data, install malware, etc.) to an active terminal session with no inherent restrictions.

From the tool's definition 'Send keys/commands to a tmux session. Automatically appends Enter unless literal mode is specified.' - this tool sends arbitrary commands to a terminal session, causing execution of whatever is typed

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

tmux_send_keys Rate-limited

tmux_send_keys 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": {
    "tmux_send_keys": {
      "limits": [
        {
          "counter": "tmux_send_keys_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 Tmux MCP Server, so you can run agents against it safely.

FAQ

Questions about tmux_send_keys

What does the tmux_send_keys tool do? +

Send keys/commands to a tmux session. Automatically appends Enter unless literal mode is specified. It is categorised as a Execute tool in the Tmux MCP Server MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on tmux_send_keys? +

Register the Tmux MCP Server MCP server in PolicyLayer and add a rule for tmux_send_keys: 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 MCP Server. Nothing to install.

What risk level is tmux_send_keys? +

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

Can I rate-limit tmux_send_keys? +

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

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

tmux_send_keys is provided by the Tmux MCP Server MCP server (mediocretriumph/tmux-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.