browser_open

THE RISK

High Risk

Why browser_open needs a policy

This tool launches or controls a browser to navigate to a specified URL, which constitutes an external operation/browser action. While it returns a screenshot (read-like), the primary action is executing a browser navigation with side effects (loading arbitrary URLs, executing page scripts, triggering network requests). Severity is medium since it operates within a sandbox but can still reach external sites.

From the tool's definition Open Chrome inside the sandbox (or navigate the existing tab) at the given URL

Documented attack patterns abuse exactly the kind of access browser_open gives an agent:

POLICY

How to control browser_open

PolicyLayer is an MCP gateway — it sits between your AI agents and Taw Computer, and nothing reaches the server without passing your rules. This is the rule we recommend for browser_open:

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "browser_open": {
      "limits": [
        {
          "counter": "browser_open_rate",
          "window": "minute",
          "max": 10,
          "scope": "grant"
        }
      ]
    }
  }
}

browser_open 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.

Create a free account and register Taw Computer — nothing to install.
Add this policy — paste it, or build it visually.
Point your MCP client (Claude, Cursor, anything) at your gateway URL.

RATE-LIMIT THIS TOOL →

Free to start. No card required.

EXPLORE

Related tools and policies

More Taw Computer tools

Destructive vm_destroy Destroy a sandbox and free its ports. By default the VM filesystem is saved as a snapshot Destructive vm_reset Reset a VM to a clean state. Destroys the current VM AND deletes its saved snapshot, so th Destructive snapshot_delete Delete a saved snapshot by label. This frees disk space and means the next vm_create with Destructive browser_close Kill all Chrome processes inside the sandbox. Execute browser_eval Run a JavaScript expression in the page context and return the result. Execute browser_navigate Navigate the sandbox Chrome to a URL via CDP (Playwright). Returns final URL and page titl Execute browser_run_test Run a Playwright test script against the browser inside a VM. Has Execute browser_wait_for Wait until a condition holds (selector visible, text appears, or network idle).

All 36 Taw Computer tools →

Execute tools on other servers

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Go deeper

High-risk tools in Taw Computer → Every high-risk tool this server exposes, in one view.
All high-risk MCP tools → Every high-risk tool across the catalogue, and the policy pattern that contains them.
The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Agent sandbox → Bounding what an agent can execute and where the boundary should sit.
Least privilege for MCP → Granting agents the minimum tool surface the task needs.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →

FAQ

Questions about browser_open

What does the browser_open tool do? +

Open Chrome inside the sandbox (or navigate the existing tab) at the given URL, then return a JPEG screenshot. It is categorised as a Execute tool in the Taw Computer MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on browser_open? +

Register the Taw Computer MCP server in PolicyLayer and add a rule for browser_open: 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 Taw Computer. Nothing to install.

What risk level is browser_open? +

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

Can I rate-limit browser_open? +

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

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

browser_open is provided by the Taw Computer MCP server (tawgroup/taw-computer). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every Taw Computer tool call.

Start from Taw Computer, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.

CHECK YOUR STACK →