Get the amount of memory available for allocating to VMs, in bytes.
AI agents call vm_available_memory to retrieve information from Truenas without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool performs a simple data retrieval operation to check available memory resources. It has no side effects, cannot modify system state, and poses minimal risk if an AI agent calls it. The worst outcome is retrieving accurate or inaccurate memory information, which does not cause harm.
From the tool's definition Tool name 'vm_available_memory' and description 'Get the amount of memory available for allocating to VMs, in bytes' indicate a read-only query operation that retrieves system information without modifying, executing, or deleting any data.
Documented attack patterns abuse exactly the kind of access vm_available_memory gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Truenas, and nothing reaches the server without passing your rules. This is the rule we recommend for vm_available_memory:
{
"version": "1",
"default": "deny",
"tools": {
"vm_available_memory": {}
}
}vm_available_memory is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
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Get the amount of memory available for allocating to VMs, in bytes. It is categorised as a Read tool in the Truenas MCP Server, which means it retrieves data without modifying state.
Register the Truenas MCP server in PolicyLayer and add a rule for vm_available_memory: 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 Truenas. Nothing to install.
vm_available_memory 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 vm_available_memory 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 vm_available_memory. 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.
vm_available_memory is provided by the Truenas MCP server (spranab/truenas-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Truenas, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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279 Truenas tools catalogued and risk-classified — across an index of 43,000+ MCP servers.