RECOMMENDED: Create hook script for function/fetch/xhr/property/cookie/websocket/eval/timer. Hooks run without pausing page execution and are the preferred approach over breakpoints for monitoring and interception.
AI agents invoke create_hook to trigger actions in JS Reverse MCP. What it does depends on the arguments the agent supplies, and its effects often reach beyond the immediate call — builds kicked off, notifications sent, workflows started.
This tool injects hook scripts into a browser at runtime, intercepting and potentially modifying behavior of fetch, XHR, eval, timers, cookies, and websockets. Injecting executable code into a running browser session is an Execute-category action with high severity, as a misused hook could intercept credentials, manipulate network traffic, or alter page behavior in ways that are difficult to detect or reverse.
From the tool's definition 'Create hook script for function/fetch/xhr/property/cookie/websocket/eval/timer. Hooks run without pausing page execution and are the preferred approach over breakpoints for monitoring and interception.'
Attacks that exploit this kind of access
RECOMMENDED: Create hook script for function/fetch/xhr/property/cookie/websocket/eval/timer. Hooks run without pausing page execution and are the preferred approach over breakpoints for monitoring and interception. It is categorised as a Execute tool in the JS Reverse MCP MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.
Register the JS Reverse MCP server in PolicyLayer and add a rule for create_hook: 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 JS Reverse MCP. Nothing to install.
create_hook is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.
Yes. Add a rate_limit block to the create_hook 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 create_hook. 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.
create_hook is provided by the JS Reverse MCP server (noone-hub/jsreverser-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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