Get a flat list of available family types in the current Revit model. Use contains to filter by a substring of the family or type name (case-insensitive).
AI agents call list_families to retrieve information from MCP server for Revit - Python without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
list_families retrieves metadata about available family types in a Revit model without modifying state, executing code, or causing side effects. It is purely informational, making it a Read category tool with low severity since misuse would only result in information disclosure, not data loss or operational damage.
From the tool's definition Tool description explicitly states 'Get a flat list' with optional filtering by substring. This is a retrieval/query operation with no modification or execution. The term 'Get' and 'list' are characteristic of Read operations.
Documented attack patterns abuse exactly the kind of access list_families gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and MCP server for Revit - Python, and nothing reaches the server without passing your rules. This is the rule we recommend for list_families:
{
"version": "1",
"default": "deny",
"tools": {
"list_families": {}
}
}list_families is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
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Get a flat list of available family types in the current Revit model. Use contains to filter by a substring of the family or type name (case-insensitive). It is categorised as a Read tool in the MCP server for Revit - Python MCP Server, which means it retrieves data without modifying state.
Register the MCP server for Revit - Python MCP server in PolicyLayer and add a rule for list_families: 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 MCP server for Revit - Python. Nothing to install.
list_families 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 list_families 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 list_families. 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.
list_families is provided by the MCP server for Revit - Python MCP server (mcp-servers-for-revit/mcp-server-for-revit-python). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from MCP server for Revit - Python, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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20 MCP server for Revit - Python tools catalogued and risk-classified — across an index of 43,000+ MCP servers.