Analyze Core Web Vitals metrics (LCP, CLS, FID/INP, TTFB) and identify problematic elements affecting these metrics. Uses Performance Observer API to provide detailed insights into real user experience metrics.
AI agents call webtool_web_vitals to retrieve information from Webtools MCP Server without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool retrieves and queries performance metrics from a webpage without side effects. It observes and reports on existing data (LCP, CLS, FID/INP, TTFB) rather than modifying, executing arbitrary operations, or destroying data. The use of Performance Observer API confirms it is a read-only measurement and analysis tool.
From the tool's definition Tool analyzes and identifies metrics using Performance Observer API; description contains verbs 'Analyze' and 'identify' with no mention of creating, modifying, executing code, deleting data, or moving money. Core Web Vitals measurement is observational.
Attacks that exploit this kind of access
Analyze Core Web Vitals metrics (LCP, CLS, FID/INP, TTFB) and identify problematic elements affecting these metrics. Uses Performance Observer API to provide detailed insights into real user experience metrics. It is categorised as a Read tool in the Webtools MCP Server MCP Server, which means it retrieves data without modifying state.
Register the Webtools MCP Server MCP server in PolicyLayer and add a rule for webtool_web_vitals: 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 Webtools MCP Server. Nothing to install.
webtool_web_vitals 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 webtool_web_vitals 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 webtool_web_vitals. 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.
webtool_web_vitals is provided by the Webtools MCP Server MCP server (misterboe/webtools-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Every MCP server has a record like this.
Type a name, get the same breakdown: verified identity, auth posture, risk grade, capabilities, recommended policy.
Teams ship this data inside their own products. See what a licence covers →