viewport_set_mode

THE RISK

High Risk

Why viewport_set_mode needs a policy

This tool modifies the state of a running browser session by changing its viewport mode. It triggers an external operation on the browser (changing the rendering context), making it Execute category. The blast radius is low since it only affects viewport dimensions in the current browser session with no data loss or financial implications.

From the tool's definition Changes viewport. mode: 'iphone', 'ipad', or 'desktop'

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

POLICY

How to control viewport_set_mode

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

policy.json

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

viewport_set_mode 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 Browser-Debugger — 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 Browser-Debugger tools

Destructive browser_close Closes browser and saves all artifacts (video, logs, screenshots, HAR, trace). Execute browser_launch 🔴 ALWAYS USE THIS FIRST - Starts browser automation. Execute media_record_video Video recording control. action: 'start' or 'stop'. Execute app_interact Universal form filler and button clicker. fields: list of values, button: button text hint Read performance_get_metrics Analyzes page performance (Core Web Vitals: LCP, FCP, CLS). Read debug_read_logs Reads console and network logs (last 20 each). Read dom_get_source Returns HTML source of current page (truncated to 5000 chars). Read dom_inspect_element Inspects element visibility, position, and attributes. Use selector OR xpath.

All 14 Browser-Debugger tools →

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Go deeper

High-risk tools in Browser-Debugger → 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 viewport_set_mode

What does the viewport_set_mode tool do? +

Changes viewport. mode: 'iphone', 'ipad', or 'desktop'. It is categorised as a Execute tool in the Browser-Debugger MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on viewport_set_mode? +

Register the Browser-Debugger MCP server in PolicyLayer and add a rule for viewport_set_mode: 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 Browser-Debugger. Nothing to install.

What risk level is viewport_set_mode? +

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

Can I rate-limit viewport_set_mode? +

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

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

viewport_set_mode is provided by the Browser-Debugger MCP server (selvadinesh-giga/mcp-based-browser-debug-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every Browser-Debugger tool call.

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

CHECK YOUR STACK →