create-session · Ryan's Tmux MCP Server MCP: Risk & Policy

WHAT IT DOES

What create-session does on Ryan's Tmux MCP Server

AI agents invoke create-session to trigger actions in Ryan's 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 create-session needs a policy

Creating a tmux session triggers an external OS-level operation that instantiates a new persistent shell environment. While not destructive or financial, it goes beyond a simple write (data creation) as it executes/spawns a live process on the host system. Misuse could lead to resource exhaustion or serve as a foothold for further command execution via sibling tools like execute-command.

From the tool's definition "Create a new tmux session" — spawns a new tmux session, which is an external system operation that creates a persistent process environment

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

create-session Rate-limited

create-session 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": {
    "create-session": {
      "limits": [
        {
          "counter": "create-session_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 Ryan's Tmux MCP Server, so you can run agents against it safely.

FAQ

Questions about create-session

What does the create-session tool do? +

Create a new tmux session. It is categorised as a Execute tool in the Ryan's 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 create-session? +

Register the Ryan's Tmux MCP Server MCP server in PolicyLayer and add a rule for create-session: 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 Ryan's Tmux MCP Server. Nothing to install.

What risk level is create-session? +

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

Can I rate-limit create-session? +

Yes. Add a rate_limit block to the create-session 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 create-session completely? +

Set action: deny in the PolicyLayer policy for create-session. 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 create-session? +

create-session is provided by the Ryan's Tmux MCP Server MCP server (ryancnelson/ryan-tmux-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.