new_tab · Hermes Computer Use MCP: Risk & Policy

WHAT IT DOES

What new_tab does on Hermes Computer Use

AI agents invoke new_tab to trigger actions in Hermes Computer Use. 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 new_tab needs a policy

This tool executes browser operations that can load arbitrary URLs and trigger page scripts/third-party content execution. While not directly destructive or financial, it can be misused to: (1) navigate to malicious sites that compromise the system, (2) trigger unintended page-based side effects (form submissions, redirects), (3) exfiltrate data through URLs.

From the tool's definition Tool description states 'Open a new Chrome tab to url' - this is a browser automation action that triggers external operations (opening URLs, potentially loading malicious content, executing JavaScript on loaded pages).

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

new_tab Rate-limited

new_tab 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": {
    "new_tab": {
      "limits": [
        {
          "counter": "new_tab_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 Hermes Computer Use, so you can run agents against it safely.

FAQ

Questions about new_tab

What does the new_tab tool do? +

Open a new Chrome tab to url. It is categorised as a Execute tool in the Hermes Computer Use MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on new_tab? +

Register the Hermes Computer Use MCP server in PolicyLayer and add a rule for new_tab: 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 Hermes Computer Use. Nothing to install.

What risk level is new_tab? +

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

Can I rate-limit new_tab? +

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

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

new_tab is provided by the Hermes Computer Use MCP server (noah3521/hermes-computer-use). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.