Constrain a line to be vertical. Args: sketch_name: Name of the sketch. geometry_index: Index of the line geometry. doc_name: Document containing the sketch. Uses active document if None. Returns: Dictionary with constraint info: - constraint_index: Index of the added constraint
AI agents use constrain_vertical 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 is a Write operation because it creates a new constraint in a FreeCAD sketch, which is a reversible modification. The constraint can be removed or modified later. It does not execute arbitrary code, delete data, or have financial implications. The blast radius is limited to the specific sketch being modified, and the action is easily undoable within FreeCAD's undo system.
From the tool's definition The tool 'constrain_vertical' modifies sketch geometry by adding a constraint to a line, as indicated by the description 'Constrain a line to be vertical' and the return of 'constraint_index: Index of the added constraint', which shows it creates a new…
Documented attack patterns abuse exactly the kind of access constrain_vertical 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_vertical:
{
"version": "1",
"default": "deny",
"tools": {
"constrain_vertical": {
"limits": [
{
"counter": "constrain_vertical_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}constrain_vertical 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 a line to be vertical. Args: sketch_name: Name of the sketch. geometry_index: Index of the line geometry. 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_vertical: 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_vertical 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_vertical 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_vertical. 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_vertical 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.