key_up · macOS Control MCP Server MCP: Risk & Policy

WHAT IT DOES

What key_up does on macOS Control MCP Server

AI agents invoke key_up to trigger actions in macOS Control 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 key_up needs a policy

Releasing a held key is a keyboard input action that executes external operations in the OS or applications. When combined with key_down, it can simulate keystrokes, trigger hotkeys, or perform other side-effecting desktop automation actions. The blast radius is medium since it can interact with any application or system function, but requires prior key_down state to be meaningful.

From the tool's definition Release a held key — part of keyboard automation that can trigger OS-level or application-level actions when used in combination with key_down

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

key_up Rate-limited

key_up 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": {
    "key_up": {
      "limits": [
        {
          "counter": "key_up_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 macOS Control MCP Server, so you can run agents against it safely.

FAQ

Questions about key_up

What does the key_up tool do? +

Release a held key. It is categorised as a Execute tool in the macOS Control 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 key_up? +

Register the macOS Control MCP Server MCP server in PolicyLayer and add a rule for key_up: 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 macOS Control MCP Server. Nothing to install.

What risk level is key_up? +

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

Can I rate-limit key_up? +

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

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

key_up is provided by the macOS Control MCP Server MCP server (lodimup/macos-control-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.