AI agents use set_sizing_system_properties 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.
The tool modifies energy model configuration (sizing properties for HVAC systems) which affects simulation inputs and results. This is a reversible data modification (Write category) rather than a destructive deletion or code execution.
From the tool's definition Tool name 'set_sizing_system_properties' indicates modification of system sizing parameters in an OpenStudio energy model.
Documented attack patterns abuse exactly the kind of access set_sizing_system_properties 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 set_sizing_system_properties:
{
"version": "1",
"default": "deny",
"tools": {
"set_sizing_system_properties": {
"limits": [
{
"counter": "set_sizing_system_properties_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}set_sizing_system_properties 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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set_sizing_system_properties. 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 set_sizing_system_properties: 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.
set_sizing_system_properties 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 set_sizing_system_properties 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 set_sizing_system_properties. 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.
set_sizing_system_properties 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.