playwright_evaluate

THE RISK

High Risk

Why playwright_evaluate needs a policy

This tool permits execution of arbitrary JavaScript within a browser context. While the blast radius is constrained to a single browser session (not system-wide shell execution), JavaScript can perform many impactful operations: steal session data, manipulate the DOM, exfiltrate credentials, trigger unwanted user interactions, or interact with sensitive web applications.

From the tool's definition Tool name: 'playwright_evaluate'. Description: 'Execute JavaScript in the browser console'. The verb 'Execute' and explicit mention of running 'JavaScript in the browser console' indicate arbitrary code execution.

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

POLICY

How to control playwright_evaluate

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

policy.json

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

playwright_evaluate 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 RunAutomation MCP Server — 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 RunAutomation MCP Server tools

Destructive clear_codegen_session Clear a code generation session without generating a test Destructive cleanup_idle_sessions Automatically close idle browser sessions that haven Destructive close_browser_session Close a specific browser session and cleanup all resources including browser instance, pag Destructive playwright_close Close the browser and release all resources Execute playwright_delete Perform an HTTP DELETE request Execute playwright_batch_ai_visual_compare Run batch AI visual comparisons across multiple pages Execute playwright_emulate_device Emulate a mobile device with specific viewport, user agent, and capabilities. Supports all Execute playwright_expect_response Ask Playwright to start waiting for a HTTP response. This tool initiates the wait operatio

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Go deeper

High-risk tools in RunAutomation MCP Server → 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 playwright_evaluate

What does the playwright_evaluate tool do? +

Execute JavaScript in the browser console. It is categorised as a Execute tool in the RunAutomation MCP Server MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on playwright_evaluate? +

Register the RunAutomation MCP Server MCP server in PolicyLayer and add a rule for playwright_evaluate: 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 RunAutomation MCP Server. Nothing to install.

What risk level is playwright_evaluate? +

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

Can I rate-limit playwright_evaluate? +

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

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

playwright_evaluate is provided by the RunAutomation MCP Server MCP server (tayyabakmal1/runautomation-mcpserver). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every RunAutomation MCP Server tool call.

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

CHECK YOUR STACK →