Constrain two lines to be parallel. Args: sketch_name: Name of the sketch. geometry1: Index of first line. geometry2: Index of second line. doc_name: Document containing the sketch. Uses active document if None. Returns: Dictionary with constraint info: - constraint_index: Index of the added cons...
AI agents use constrain_parallel 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 a new constraint in a sketch, which is a reversible modification of the document state. It does not delete data (would be Destructive), execute arbitrary code (would be Execute), or involve financial operations. The constraint can be removed or modified later, making it a Write operation with low severity since the blast radius is limited to geometric sketch constraints that can be easily undone.
From the tool's definition Tool modifies sketch constraints by adding a parallel constraint between two lines, which creates a new constraint object in the FreeCAD document.
Documented attack patterns abuse exactly the kind of access constrain_parallel 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 constrain_parallel:
{
"version": "1",
"default": "deny",
"tools": {
"constrain_parallel": {
"limits": [
{
"counter": "constrain_parallel_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}constrain_parallel 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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Constrain two lines to be parallel. Args: sketch_name: Name of the sketch. geometry1: Index of first line. geometry2: Index of second line. doc_name: Document containing the sketch. Uses active document if None. Returns: Dictionary with constraint info: - constraint_index: Index of the added constraint. 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 constrain_parallel: 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.
constrain_parallel 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 constrain_parallel 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 constrain_parallel. 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.
constrain_parallel 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.