Assert that an element exists by selector or inspected element id.
AI agents call assert_element_exists to retrieve information from Visual Annotation MCP 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 — a read/query operation with no side effects. It returns a pass/fail assertion result without modifying any state.
From the tool's definition Assert that an element exists by selector or inspected element id
Attacks that exploit this kind of access
Assert that an element exists by selector or inspected element id. It is categorised as a Read tool in the Visual Annotation MCP MCP Server, which means it retrieves data without modifying state.
Register the Visual Annotation MCP server in PolicyLayer and add a rule for assert_element_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 Visual Annotation MCP. Nothing to install.
assert_element_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 assert_element_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 assert_element_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.
assert_element_exists is provided by the Visual Annotation MCP server (mstocker1/visual_annotation_mcp). 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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