open_tab · Nextjs Agent MCP: Risk & Policy

WHAT IT DOES

What open_tab does on Nextjs Agent

AI agents invoke open_tab to trigger actions in Nextjs Agent. 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 open_tab needs a policy

Opening a browser tab is an external operation that triggers real browser actions. While not destructive or financial, it executes a browser-level command that causes side effects (new tab, navigation, potential page loads), placing it in the Execute category. Misuse could lead to navigating to malicious URLs or causing unintended interactions with the Next.js app.

From the tool's definition Open a new browser tab at — triggers an external browser operation (opening a tab), which is a real side effect in a running browser environment

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

open_tab Rate-limited

open_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": {
    "open_tab": {
      "limits": [
        {
          "counter": "open_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 Nextjs Agent, so you can run agents against it safely.

FAQ

Questions about open_tab

What does the open_tab tool do? +

Open a new browser tab at. It is categorised as a Execute tool in the Nextjs Agent MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on open_tab? +

Register the Nextjs Agent MCP server in PolicyLayer and add a rule for open_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 Nextjs Agent. Nothing to install.

What risk level is open_tab? +

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

Can I rate-limit open_tab? +

Yes. Add a rate_limit block to the open_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 open_tab completely? +

Set action: deny in the PolicyLayer policy for open_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 open_tab? +

open_tab is provided by the Nextjs Agent MCP server (zohaib3249/nextjs-agent-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.