freecad-mcp

create_sketch

Create an empty sketch on a PartDesign Body's XY, XZ, or YZ plane to hold constrained 2D geometry for later padding or pocketing.

Instructions

Create an empty sketch attached to one of a PartDesign Body's base planes.

plane is one of "XY", "XZ", "YZ". Populate it with add_rectangle/
add_circle/add_polygon (each one locks its own geometry so the sketch
stays fully constrained), then pad or pocket it.

Args:
    doc_name: The name of the document.
    body_name: The name of the existing PartDesign::Body to sketch in.
    name: The name to give the new sketch.
    plane: Which base plane to attach to: "XY", "XZ", or "YZ".

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "doc_name": "<doc_name>",
      "body_name": "<body_name>",
      "name": "<name>"
    },
    "name": "create_sketch"
  }
}

Input Schema

Name	Required	Default
`name`	Yes
`plane`	No	XY
`doc_name`	Yes
`body_name`	Yes

Output Schema

Name	Required	Description	Default
`result`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.1.19Aug 1, 2026

TDQS

A4.3/5.0

Behavior3/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

With no annotations, the description carries the burden of safety disclosure. It states that the body must already exist ('existing PartDesign::Body') and constrains plane to three values, giving useful preconditions. However, it does not explicitly state that this write operation modifies the document, nor does it cover failure cases or whether the operation is reversible.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is a compact summary plus an Args block, with no redundant phrasing. The opening sentence captures the core action, and the workflow sentence is informative.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness4/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given the existence of an output schema, the description doesn't need to explain return values. It provides the essential workflow, parameter meanings, and a pointer to subsequent operations. Missing details like error handling are understandable for a CAD tool, but the core invocation is well covered.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters5/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

The Args section adds one-line explanations for each parameter, including the exact allowed plane strings, which the schema leaves unspecified. This fully compensates for the schema's lack of parameter descriptions.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the tool creates an empty sketch attached to a PartDesign Body's base plane, and explicitly names the accepted plane values. This distinguishes it from sibling tools like add_rectangle or pad, which operate on the sketch.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description tells the agent to populate the sketch with add_rectangle/add_circle/add_polygon and then pad or pocket, providing a clear sequence. It doesn't explicitly say when to use this over alternatives, but the workflow strongly implies its role as the initial sketch-creation step.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.