Analyze page complexity and performance characteristics. Reports on: iframe count, DOM size, modal states, element statistics. Use for: debugging slow pages, understanding page structure, or monitoring page complexity.
AI agents call browser_diagnose to retrieve information from Fast Playwright MCP without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool only reads and reports diagnostic information about the current page (iframe count, DOM size, modal states, element statistics). It has no side effects and does not modify, execute, or delete anything. It is purely observational/analytical.
From the tool's definition Analyze page complexity and performance characteristics. Reports on: iframe count, DOM size, modal states, element statistics.
Documented attack patterns abuse exactly the kind of access browser_diagnose 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_diagnose:
{
"version": "1",
"default": "deny",
"tools": {
"browser_diagnose": {}
}
}browser_diagnose is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
Free to start. No card required.
Analyze page complexity and performance characteristics. Reports on: iframe count, DOM size, modal states, element statistics. Use for: debugging slow pages, understanding page structure, or monitoring page complexity. It is categorised as a Read tool in the Fast Playwright MCP MCP Server, which means it retrieves data without modifying state.
Register the Fast Playwright MCP server in PolicyLayer and add a rule for browser_diagnose: 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_diagnose is a Read tool with low risk. Read-only tools are generally safe to allow by default.
Yes. Add a rate_limit block to the browser_diagnose 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_diagnose. 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_diagnose 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.