True if at least one element matches the selector. Zero-round-trip
AI agents call dom_exists to retrieve information from Hermes Computer Use without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool only checks for the existence of a DOM element matching a selector and returns a boolean. It reads browser state without modifying anything, executing code, or causing any side effects.
From the tool's definition 'True if at least one element matches the selector. Zero-round-trip' — purely queries DOM state with no side effects
Attacks that exploit this kind of access
True if at least one element matches the selector. Zero-round-trip. It is categorised as a Read tool in the Hermes Computer Use MCP Server, which means it retrieves data without modifying state.
Register the Hermes Computer Use MCP server in PolicyLayer and add a rule for dom_exists: 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 Hermes Computer Use. Nothing to install.
dom_exists 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 dom_exists 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 dom_exists. 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.
dom_exists is provided by the Hermes Computer Use MCP server (noah3521/hermes-computer-use). 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.
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