get_rectangle_of_screen

THE RISK

Low Risk

Why get_rectangle_of_screen needs a policy

This tool retrieves visual data from a designated screen region. While the description is empty, the name and context of sibling screen-capture tools strongly suggest it performs OCR or image capture of a rectangle—a read-only operation with no side effects.

From the tool's definition Tool name 'get_rectangle_of_screen' and sibling tools 'get_text_from_rectangle_of_screen', 'get_whole_screen_image', 'get_text_from_whole_screen_image' indicate screen reading/retrieval functions.

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

POLICY

How to control get_rectangle_of_screen

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

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "get_rectangle_of_screen": {}
  }
}

get_rectangle_of_screen is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.

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

CAP THIS TOOL →

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EXPLORE

Related tools and policies

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All 20 Vnc tools →

Read tools on other servers

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Go deeper

The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Data exfiltration → How read access becomes an exfiltration channel when chained with untrusted content.
MCP token cost → What connecting this server costs in context-window tokens on every request.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →

FAQ

Questions about get_rectangle_of_screen

What does the get_rectangle_of_screen tool do? +

get_rectangle_of_screen. It is categorised as a Read tool in the Vnc MCP Server, which means it retrieves data without modifying state.

How do I enforce a policy on get_rectangle_of_screen? +

Register the Vnc MCP server in PolicyLayer and add a rule for get_rectangle_of_screen: 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 Vnc. Nothing to install.

What risk level is get_rectangle_of_screen? +

get_rectangle_of_screen is a Read tool with low risk. Read-only tools are generally safe to allow by default.

Can I rate-limit get_rectangle_of_screen? +

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

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

get_rectangle_of_screen is provided by the Vnc MCP server (regulad/vnc-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every Vnc tool call.

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

CHECK YOUR STACK →