Get the full accessibility/UI tree as structured JSON.
AI agents call get_ui_tree to retrieve information from App Screen without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool retrieves and returns structured data about the current UI state without modifying the simulator, app state, or any data. It is purely informational and supports the observe phase of the observe-reason-act cycle. The accessibility tree is metadata about the UI, not sensitive user data or system state that would elevate risk.
From the tool's definition Tool description states 'Get the full accessibility/UI tree as structured JSON' — a retrieval operation with no modification or side effects. The verb 'Get' indicates a read-only query.
Attacks that exploit this kind of access
Get the full accessibility/UI tree as structured JSON. It is categorised as a Read tool in the App Screen MCP Server, which means it retrieves data without modifying state.
Register the App Screen MCP server in PolicyLayer and add a rule for get_ui_tree: 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 App Screen. Nothing to install.
get_ui_tree 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_ui_tree 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_ui_tree. 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_ui_tree is provided by the App Screen MCP server (xmuweili/app-screen-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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