Выполнить JavaScript код в указанной вкладке
AI agents invoke evaluate to trigger actions in Yandex Browser MCP Server. 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.
Executing arbitrary JavaScript in a browser tab is the definition of Execute category. The blast radius is critical because arbitrary JS can access cookies, localStorage, perform DOM manipulation, exfiltrate data, trigger navigation, or interact with any web content. There are no reversibility constraints — any side effects depend entirely on the code passed as argument.
From the tool's definition "Выполнить JavaScript код" means "Execute JavaScript code" — the tool runs arbitrary JavaScript in a browser tab
Documented attack patterns abuse exactly the kind of access evaluate gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Yandex Browser MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for evaluate:
{
"version": "1",
"default": "deny",
"tools": {
"evaluate": {
"limits": [
{
"counter": "evaluate_rate",
"window": "minute",
"max": 10,
"scope": "grant"
}
]
}
}
}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.
Free to start. No card required.
Выполнить JavaScript код в указанной вкладке. It is categorised as a Execute tool in the Yandex Browser MCP Server MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.
Register the Yandex Browser MCP Server MCP server in PolicyLayer and add a rule for 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 Yandex Browser MCP Server. Nothing to install.
evaluate 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 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. 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 is provided by the Yandex Browser MCP Server MCP server (t1trit/yandex-browser-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Yandex Browser MCP Server, 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.
18 Yandex Browser MCP Server tools catalogued and risk-classified — across an index of 43,000+ MCP servers.