Execute JavaScript code in the context of the current page. The code runs in the page
AI agents invoke javascript_tool to trigger actions in OpenChrome. What it does depends on the arguments the agent supplies, and its effects often reach beyond the immediate call — builds kicked off, notifications sent, workflows started.
This tool runs JavaScript directly in a browser context, which can read/modify the DOM, access local storage, cookies, execute API calls, redirect pages, or trigger any client-side action.
From the tool's definition Tool description states 'Execute JavaScript code in the context of the current page. The code runs in the page' - direct execution of arbitrary code.
Documented attack patterns abuse exactly the kind of access javascript_tool gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and OpenChrome, and nothing reaches the server without passing your rules. This is the rule we recommend for javascript_tool:
{
"version": "1",
"default": "deny",
"tools": {
"javascript_tool": {
"limits": [
{
"counter": "javascript_tool_rate",
"window": "minute",
"max": 10,
"scope": "grant"
}
]
}
}
}javascript_tool 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.
Free to start. No card required.
Execute JavaScript code in the context of the current page. The code runs in the page. It is categorised as a Execute tool in the OpenChrome MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.
Register the OpenChrome MCP server in PolicyLayer and add a rule for javascript_tool: 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 OpenChrome. Nothing to install.
javascript_tool 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 javascript_tool 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 javascript_tool. 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.
javascript_tool is provided by the OpenChrome MCP server (shaun0927/openchrome). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 106 OpenChrome tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
Free to start. No card required.
106 OpenChrome tools catalogued and risk-classified — across an index of 42,500+ MCP servers.