Creates a sketch inside a Body on an origin or datum plane. Returns the sketch handle and name for subsequent modeling.
Create a sketch in a Body, attached to a plane.
plane: 'XY' | 'XZ' | 'YZ' for origin planes, or a datum-plane handle. Returns {handle, name}.
| Name | Required | Description | Default |
|---|---|---|---|
| body | Yes | ||
| name | No | Sketch | |
| plane | No | XY |
Changes observed during successful MCP inspections.
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations are provided, so the description carries the full burden. It helpfully discloses the return shape (Returns {handle, name}) and the accepted plane inputs, but says nothing about prerequisites (does the body need to exist), transaction/document-mutation semantics, or name handling beyond the schema default.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
Front-loaded with the action, then the plane options, then the return value. Compact and waste-free; every clause adds usable information.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
For a creation tool with no output schema and no annotations, it covers the plane choices and the return shape reasonably, but omits the required body parameter's meaning, preconditions, and document/transaction effects, leaving gaps an agent would need.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
Schema description coverage is 0%, so the description must compensate. It documents the 'plane' parameter well (enumerating 'XY'|'XZ'|'YZ' plus the datum-plane-handle option), which is meaningful beyond the bare schema, but leaves the required 'body' and optional 'name' parameters completely unexplained.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
States a specific verb+resource (create a sketch) plus its anchoring context (in a Body, attached to a plane), which distinguishes it from siblings like add_sketch_geometry, add_sketch_constraint, and close_sketch. Clear, though it doesn't explicitly name an alternative tool.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
Usage is implied by 'create a sketch in a Body, attached to a plane' but there is no explicit when-to-use, when-not-to-use, or named alternative (e.g. make_datum_plane before this, close_sketch after). An agent can infer the role but gets no routing guidance.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.