get_computed_styles
Retrieve computed CSS styles for a DOM element. Calculates and returns all computed CSS properties for the specified DOM element. This includes styles from all sources (stylesheets, inline styles, user agent styles) after CSS cascade resolution, inheritance, and computation of values. The compute...
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What get_computed_styles does on Chrome Devtools
AI agents call get_computed_styles to retrieve information from Chrome Devtools without modifying anything. It is typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
Why get_computed_styles is rated Low
This tool performs passive inspection of DOM element styling information. It retrieves and calculates computed CSS values without modifying any state, executing arbitrary code, deleting data, or triggering side effects. The operation is purely informational and has no blast radius if misused by an agent—the worst outcome would be unnecessary API calls or information disclosure about page styling.
From the tool's definition Tool description states it 'Retrieve[s] computed CSS styles for a DOM element' and 'returns all computed CSS properties'. The verb 'retrieve' and 'returns' indicate data querying with no modification, deletion, or code execution.
Attacks that exploit this kind of access
The rule that runs get_computed_styles safely
PolicyLayer is an MCP gateway: it sits between your AI agents and Chrome Devtools, and checks every tool call against a rule you set before the call runs. Nothing changes on the server itself. For get_computed_styles, this is the rule to start with:
get_computed_styles is read-only, so it stays allowed. Everything else on the server is denied unless you say otherwise.
The button opens the PolicyLayer dashboard: create your workspace, connect Chrome Devtools, apply this rule, and every get_computed_styles call is checked against it from then on.
Questions about get_computed_styles
Retrieve computed CSS styles for a DOM element. Calculates and returns all computed CSS properties for the specified DOM element. This includes styles from all sources (stylesheets, inline styles, user agent styles) after CSS cascade resolution, inheritance, and computation of values. The computed styles represent the final values that the browser uses for rendering, taking into account all CSS rules, inheritance, and default values. Args: node_id: DOM node ID of the target element. Must be a valid node ID obtained from DOM inspection tools. Returns: Computed styles dictionary containing: - success: Boolean indicating operation success - message: Summary of computed properties retrieved - data: Style information including: - nodeId: The target element's node ID - styles: Dictionary of CSS property names to computed values - totalProperties: Count of computed CSS properties Note: Computed values may differ from authored values due to CSS processing, inheritance, and browser-specific calculations. It is categorised as a Read tool in the Chrome Devtools MCP Server, which means it retrieves data without modifying state.
Register the Chrome Devtools MCP server in PolicyLayer and add a rule for get_computed_styles: 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 Chrome Devtools. Nothing to install.
get_computed_styles 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 get_computed_styles 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 get_computed_styles. 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.
get_computed_styles is provided by the Chrome Devtools MCP server (benjaminr/chrome-devtools-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
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