v8_function_retained
Find all heap objects retained by functions matching a name pattern. Walks the dominator tree to find objects whose constructor/class name matches the given pattern, then returns each with its retainer chain. Useful for understanding which objects a specific function/class is holding alive.
This record as markdown: /tools/io-github-vmoranv-jshookmcp/v8-function-retained.md
What v8_function_retained does on Jshookmcp
AI agents call v8_function_retained to retrieve information from Jshookmcp without modifying anything. It is typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
Why v8_function_retained is rated Low
Reads heap memory inspection data without modifying, deleting, or executing code.
From the tool's definition Find all heap objects retained by functions. Walks dominator tree, returns retainer chain.
Attacks that exploit this kind of access
The rule that runs v8_function_retained safely
PolicyLayer is an MCP gateway: it sits between your AI agents and Jshookmcp, and checks every tool call against a rule you set before the call runs. Nothing changes on the server itself. For v8_function_retained, this is the rule to start with:
v8_function_retained is read-only, so it stays allowed. Everything else on the server is denied unless you say otherwise.
The button opens the PolicyLayer dashboard: create your workspace, connect Jshookmcp, apply this rule, and every v8_function_retained call is checked against it from then on.
Questions about v8_function_retained
Find all heap objects retained by functions matching a name pattern. Walks the dominator tree to find objects whose constructor/class name matches the given pattern, then returns each with its retainer chain. Useful for understanding which objects a specific function/class is holding alive. It is categorised as a Read tool in the Jshookmcp MCP Server, which means it retrieves data without modifying state.
Register the Jshook MCP server in PolicyLayer and add a rule for v8_function_retained: 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 Jshookmcp. Nothing to install.
v8_function_retained 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 v8_function_retained 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 v8_function_retained. 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.
v8_function_retained is provided by the Jshook MCP server (@jshookmcp/jshook). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
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