Detect likely viewport blockers (modals/overlays) and return JSON metadata.
AI agents call detect_blockers 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 retrieves information about the current state of the page (modals/overlays) and returns structured data. It has no side effects, does not modify the page, does not execute code, and does not delete or move data. It is a read-only inspection tool that helps an agent understand the page layout.
From the tool's definition Tool detects and returns metadata about viewport blockers without modifying, deleting, or executing any operations. It 'detect[s]' and 'return[s] JSON metadata'—purely observational.
Attacks that exploit this kind of access
Detect likely viewport blockers (modals/overlays) and return JSON metadata. 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 detect_blockers: 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.
detect_blockers 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 detect_blockers 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 detect_blockers. 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.
detect_blockers 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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