Execute JavaScript code in the page context.
AI agents invoke evaluate_js to trigger actions in OODA Computer Control. 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 allows arbitrary JavaScript execution within a page context, which can modify DOM, exfiltrate data, perform financial transactions, interact with APIs, or trigger other client-side actions. The effects are entirely dependent on the JavaScript code executed, making this a dangerous Execute-category tool.
From the tool's definition Tool name 'evaluate_js' combined with description 'Execute JavaScript code in the page context' explicitly indicates code execution capabilities.
Documented attack patterns abuse exactly the kind of access evaluate_js gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and OODA Computer Control, and nothing reaches the server without passing your rules. This is the rule we recommend for evaluate_js:
{
"version": "1",
"default": "deny",
"tools": {
"evaluate_js": {
"limits": [
{
"counter": "evaluate_js_rate",
"window": "minute",
"max": 10,
"scope": "grant"
}
]
}
}
}evaluate_js 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 page context. It is categorised as a Execute tool in the OODA Computer Control MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.
Register the OODA Computer Control MCP server in PolicyLayer and add a rule for evaluate_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 OODA Computer Control. Nothing to install.
evaluate_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 evaluate_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 evaluate_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.
evaluate_js is provided by the OODA Computer Control MCP server (mnehmos/mnehmos.ooda.mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from OODA Computer Control, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
Free to start. No card required.
99 OODA Computer Control tools catalogued and risk-classified — across an index of 43,000+ MCP servers.