AI agents invoke browser_resize to trigger actions in Fast Playwright MCP. 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.
Resizing the browser window is a browser action/operation that modifies the browser's state. It falls under Execute as it triggers an external operation. The blast radius is low since it only affects viewport dimensions and has no data loss or financial implications.
From the tool's definition 'Resize the browser window' — triggers an external browser operation that changes the state of the browser viewport
Documented attack patterns abuse exactly the kind of access browser_resize gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Fast Playwright MCP, and nothing reaches the server without passing your rules. This is the rule we recommend for browser_resize:
{
"version": "1",
"default": "deny",
"tools": {
"browser_resize": {
"limits": [
{
"counter": "browser_resize_rate",
"window": "minute",
"max": 10,
"scope": "grant"
}
]
}
}
}browser_resize 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.
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Resize the browser window. It is categorised as a Execute tool in the Fast Playwright MCP MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.
Register the Fast Playwright MCP server in PolicyLayer and add a rule for browser_resize: 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 Fast Playwright MCP. Nothing to install.
browser_resize 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 browser_resize 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 browser_resize. 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.
browser_resize is provided by the Fast Playwright MCP server (tontoko/fast-playwright-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 34 Fast Playwright MCP tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
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34 Fast Playwright MCP tools catalogued and risk-classified — across an index of 42,500+ MCP servers.