Add a B-spline curve to a sketch. Args: sketch_name: Name of the sketch to add B-spline to. points: List of control points, each as [x, y]. closed: Whether to close the spline. Defaults to False. doc_name: Document containing the sketch. Uses active document if None. Returns: Dictionary with geom...
AI agents use add_sketch_bspline to create or update resources in FreeCAD Robust MCP Server — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your FreeCAD Robust MCP Server environment.
This tool creates or modifies 3D model data within FreeCAD by adding a geometric element to a sketch. It does not execute arbitrary code, delete data, or cause financial effects. The operation is reversible (the B-spline can be deleted or modified). The blast radius is limited to the active sketch within FreeCAD's model, affecting only the design document in memory. This clearly falls under the Write category.
From the tool's definition The tool creates a B-spline curve within a sketch by adding a new geometry element. The description explicitly states 'Add a B-spline curve to a sketch' and returns geometry metadata including the index of the newly added element.
Documented attack patterns abuse exactly the kind of access add_sketch_bspline gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and FreeCAD Robust MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for add_sketch_bspline:
{
"version": "1",
"default": "deny",
"tools": {
"add_sketch_bspline": {
"limits": [
{
"counter": "add_sketch_bspline_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}add_sketch_bspline 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.
Free to start. No card required.
Add a B-spline curve to a sketch. Args: sketch_name: Name of the sketch to add B-spline to. points: List of control points, each as [x, y]. closed: Whether to close the spline. Defaults to False. doc_name: Document containing the sketch. Uses active document if None. Returns: Dictionary with geometry info: - geometry_index: Index of the added B-spline - geometry_count: Total geometry elements. It is categorised as a Write tool in the FreeCAD Robust MCP Server MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the FreeCAD Robust MCP Server MCP server in PolicyLayer and add a rule for add_sketch_bspline: 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 FreeCAD Robust MCP Server. Nothing to install.
add_sketch_bspline 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_sketch_bspline 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_sketch_bspline. 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_sketch_bspline is provided by the FreeCAD Robust MCP Server MCP server (spkane/freecad-addon-robust-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 152 FreeCAD Robust MCP Server tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
Free to start. No card required.
152 FreeCAD Robust MCP Server tools catalogued and risk-classified — across an index of 42,500+ MCP servers.