Execute arbitrary JavaScript in the current tab and return the result. Use this for complex DOM queries, CSS selector extraction, or any operation that would take multiple DOMShell commands.\n\nThe code runs in the page context with full DOM access. Promises are automatically awaited. Results are...
Part of the DOMShell server.
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AI agents invoke domshell_js to trigger processes or run actions in DOMShell. 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.
domshell_js can trigger processes with real-world consequences. An uncontrolled agent might start dozens of builds, send mass notifications, or kick off expensive compute jobs. PolicyLayer enforces rate limits and validates arguments to keep execution within safe bounds.
Execute tools trigger processes. Rate-limit and validate arguments to prevent unintended side effects.
{
"version": "1",
"default": "deny",
"tools": {
"domshell_js": {
"limits": [
{
"counter": "domshell_js_rate",
"window": "minute",
"max": 10,
"scope": "grant"
}
]
}
}
}See the full DOMShell policy for all 38 tools.
These attack patterns abuse exactly the kind of access domshell_js gives an agent. Each links to the full case and the policy that stops it:
Other execute tools across the catalogue. The same approach applies to each: rate-limit and validate the arguments.
Execute arbitrary JavaScript in the current tab and return the result. Use this for complex DOM queries, CSS selector extraction, or any operation that would take multiple DOMShell commands.\n\nThe code runs in the page context with full DOM access. Promises are automatically awaited. Results are JSON-serialized (truncated at 10000 chars).\n\nCommon patterns:\n js document.title\n js document.querySelectorAll(. It is categorised as a Execute tool in the DOMShell MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.
Register the DOMShell MCP server in PolicyLayer and add a rule for domshell_js: 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 DOMShell. Nothing to install.
domshell_js is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.
Yes. Add a rate_limit block to the domshell_js 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.
Set action: deny in the PolicyLayer policy for domshell_js. 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.
domshell_js is provided by the DOMShell MCP server (@apireno/domshell). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 38 DOMShell tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
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