AI agents invoke browser_tab_select 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.
Selecting a tab changes the browser's active state and can cause navigation or script execution depending on what the tab contains. It's a browser action with side effects, placing it in the Execute category. Misuse could direct the agent's context to unintended pages.
From the tool's definition 'Select a tab by index' — triggers a browser tab switch action, which is an external browser operation
Documented attack patterns abuse exactly the kind of access browser_tab_select 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_tab_select:
{
"version": "1",
"default": "deny",
"tools": {
"browser_tab_select": {
"limits": [
{
"counter": "browser_tab_select_rate",
"window": "minute",
"max": 10,
"scope": "grant"
}
]
}
}
}browser_tab_select 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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Select a tab by index. 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_tab_select: 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_tab_select 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_tab_select 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_tab_select. 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_tab_select 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.
Free to start. No card required.
34 Fast Playwright MCP tools catalogued and risk-classified — across an index of 42,500+ MCP servers.