AI agents use add_vrf_system to create or update resources in Openstudio — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Openstudio environment.
This tool creates or adds a new VRF system component to an energy simulation model, which is a reversible Write operation. While the description is empty (reducing confidence), the naming convention and context from sibling tools strongly indicate model modification rather than destruction, execution, or retrieval.
From the tool's definition Tool name 'add_vrf_system' indicates creation/modification of VRF (Variable Refrigerant Flow) HVAC system in an OpenStudio energy model.
Documented attack patterns abuse exactly the kind of access add_vrf_system gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Openstudio, and nothing reaches the server without passing your rules. This is the rule we recommend for add_vrf_system:
{
"version": "1",
"default": "deny",
"tools": {
"add_vrf_system": {
"limits": [
{
"counter": "add_vrf_system_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}add_vrf_system stays usable, but capped — an agent stuck in a loop can't make hundreds of changes a minute. Everything else on the server is denied unless you say otherwise.
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add_vrf_system. It is categorised as a Write tool in the Openstudio MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Openstudio MCP server in PolicyLayer and add a rule for add_vrf_system: 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 Openstudio. Nothing to install.
add_vrf_system is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.
Yes. Add a rate_limit block to the add_vrf_system 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 add_vrf_system. 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.
add_vrf_system is provided by the Openstudio MCP server (natlabrockies/openstudio-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Openstudio, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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146 Openstudio tools catalogued and risk-classified — across an index of 43,000+ MCP servers.