// MCP TOOL REFERENCE

evaluate_script

Execute arbitrary JavaScript on the page

Full code execution in browser context

Part of the Chrome DevTools MCP server. Enforce policies on this tool with Intercept, the open-source MCP proxy.

@ChromeDevTools/chrome-devtools-mcp Execute Risk 5/5

// WHEN AI AGENTS USE THIS TOOL

AI agents invoke evaluate_script to trigger processes or run actions in Chrome DevTools. Execute operations can have side effects beyond the immediate call -- triggering builds, sending notifications, or starting workflows. Rate limits and argument validation are essential to prevent runaway execution.

// WHY ENFORCE A POLICY ON EVALUATE_SCRIPT

evaluate_script can trigger processes with real-world consequences. An uncontrolled agent might start dozens of builds, send mass notifications, or kick off expensive compute jobs. Intercept enforces rate limits and validates arguments to keep execution within safe bounds.

// RECOMMENDED POLICY

Execute tools trigger processes. Rate-limit and validate arguments to prevent unintended side effects.

chrome-devtools.yaml

tools:
  evaluate_script:
    rules:
      - action: allow
        rate_limit:
          max: 10
          window: 60
        validate:
          required_args: true

See the full Chrome DevTools policy for all 29 tools.

// DETAILS

Tool Name evaluate_script

Category Execute

MCP Server Chrome DevTools MCP Server

Risk Level High

// MORE CHROME DEVTOOLS TOOLS

Destructive close_page Execute click Execute drag Execute emulate Execute fill Execute fill_form Execute handle_dialog Execute hover

View all 29 tools →

// WHAT CAN GO WRONG

Agents calling execute-class tools like evaluate_script have been implicated in these attack patterns. Read the full case and prevention policy for each:

Browse the full MCP Attack Database →

// OTHER EXECUTE TOOLS ACROSS MCP SERVERS

Other tools in the Execute risk category across the catalogue. The same policy patterns (rate-limit, validate) apply to each.

Agent Passport System — Cryptographic Identity for AI Agents commerce_preflight Agent Passport System — Cryptographic Identity for AI Agents execute_with_context Agent Passport System — Cryptographic Identity for AI Agents gateway_execute_approval Agent Passport System — Cryptographic Identity for AI Agents governance_360 Agent Passport System — Cryptographic Identity for AI Agents parse_governance_block_html AgentClear — API Marketplace for AI Agents call_service

// IN CONTEXT OF HIGH RISK

evaluate_script is one of the high-risk operations in Chrome DevTools. For the full severity-focused view — only the high-risk tools with their recommended policies — see the breakdown for this server, or browse all high-risk tools across every MCP server.

// RELATED READING

// FAQ

What does the evaluate_script tool do? +

Execute arbitrary JavaScript on the page. It is categorised as a Execute tool in the Chrome DevTools MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on evaluate_script? +

Add a rule in your Intercept YAML policy under the tools section for evaluate_script. You can allow, deny, rate-limit, or validate arguments. Then run Intercept as a proxy in front of the Chrome DevTools MCP server.

What risk level is evaluate_script? +

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

Can I rate-limit evaluate_script? +

Yes. Add a rate_limit block to the evaluate_script rule in your Intercept 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 evaluate_script completely? +

Set action: deny in the Intercept policy for evaluate_script. 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 evaluate_script? +

evaluate_script is provided by the Chrome DevTools MCP server (@ChromeDevTools/chrome-devtools-mcp). Intercept sits as a proxy in front of this server to enforce policies before tool calls reach the server.

evaluate_script

Enforce policies on Chrome DevTools