Compare current runner UI state against a saved bookmark (Control mode). Returns appeared, disappeared, and modified elements.
AI agents call ui_diff_from_bookmark to retrieve information from UI Bridge MCP without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
The tool performs a comparison operation that retrieves UI state information and returns differences. It has no side effects, does not modify data, does not execute code or commands, and does not delete or create resources. This is a classic Read operation similar to 'get' or 'query' that gathers information for inspection purposes.
From the tool's definition Tool description states it 'Compare[s] current runner UI state against a saved bookmark' and 'Returns appeared, disappeared, and modified elements.' This is purely a query operation that retrieves and compares UI state without modifying or executing actions.
Attacks that exploit this kind of access
Compare current runner UI state against a saved bookmark (Control mode). Returns appeared, disappeared, and modified elements. It is categorised as a Read tool in the UI Bridge MCP MCP Server, which means it retrieves data without modifying state.
Register the UI Bridge MCP server in PolicyLayer and add a rule for ui_diff_from_bookmark: 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 UI Bridge MCP. Nothing to install.
ui_diff_from_bookmark 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 ui_diff_from_bookmark 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 ui_diff_from_bookmark. 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.
ui_diff_from_bookmark is provided by the UI Bridge MCP server (qontinui/ui-bridge-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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