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OwlCAD

by com.owlcad.mcp
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Measure a model

measure
Read-onlyIdempotent

Exact volume, surface area, centre of mass and connected-body count, plus an estimate of the filament a print would consume and what it would cost. Use it to answer "how heavy / how much material / how much filament / how much will this cost" — nothing else reports those, and they cannot be derived from a bounding box. Also checks a model is ONE body — two bodies where you expected one means operands that never touched.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
scadNoOpenSCAD source, as an alternative to `nodes` (supply exactly one). Interpreted by the same engine the editor’s .scad import uses; BOSL2/MCAD includes resolve. minkowski() and resize() are not supported here — use hull() or offset().
nodesNoParametric node tree. mm, Z-up, rotations in DEGREES (a rotation.* binding: radians). Read owlcad://schema/primitives for every primitive, modifier and generator and its parameter ranges (unknown params are dropped silently), and owlcad://schema/conventions for the placement arithmetic, which is where most models go wrong.
infillNoInfill density 0–1 (default 0.15).
shellMmNoSolid skin thickness in mm (default 1.2).
projectIdNoId of one of your saved projects, as an alternative to `nodes`/`scad` (supply exactly one).
materialIdNoFilament to cost it against (default "pla"). Ids come from the owlcad://materials resource.
smoothnessNoCurve quality for shapes that left their segment count automatic. Defaults to "standard", which is the editor default — pass "high" to match a project authored at high smoothness, "draft" for a cheaper check.

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed1 schema field changed
    • changedInput schema / properties / nodes / description
      Previous value: -"Parametric node tree. mm, Z-up, rotations in DEGREES. Read owlcad://schema/primitives for every primitive, modifier and generator and its parameter ranges (unknown params are dropped silently), and owlcad://schema/conventions for the placement arithmetic, which is where most models go wrong."New value: +"Parametric node tree. mm, Z-up, rotations in DEGREES (a rotation.* binding: radians). Read owlcad://schema/primitives for every primitive, modifier and generator and its parameter ranges (unknown params are dropped silently), and owlcad://schema/conventions for the placement arithmetic, which is where most models go wrong."
  2. Changed1 schema field changed
    • changedInput schema / properties / nodes / items / properties / generatorKey / description
      Previous value: -"Generator to expand (kind=generator). PREFER one over hand-building the same thing — they carry standards dimensions and solve fits a tree of primitives gets subtly wrong: gearTrain · planetary · rackPinion · wormDrive · herringbone · herringboneTrain · pulley · bearing · belt · spring · adapter · boardMount · enclosure · gridfinity · threadedJar · pinHinge · snapFit · ballSocket · fastener · textPlate · fitCoupon · calibrationBlock · clamp · impeller · axialFan · fanFrame · plugCap."New value: +"Generator to expand (kind=generator). PREFER one over hand-building the same thing — they carry standards dimensions and solve fits a tree of primitives gets subtly wrong: gearTrain · planetary · rackPinion · wormDrive · herringbone · herringboneTrain · pulley · bearing · belt · spring · adapter · boardMount · enclosure · gridfinity · threadedJar · pinHinge · snapFit · ballSocket · fastener · textPlate · fitCoupon · calibrationBlock · clamp · impeller · axialFan · fanFrame · plugCap · pillowBlock."
  3. Changed1 schema field changed
    • changedInput schema / properties / scad / description
      Previous value: -"OpenSCAD source, as an alternative to `nodes` (supply exactly one). Interpreted by the same engine the editor’s .scad import uses. minkowski() and resize() are not supported here — use hull() or offset()."New value: +"OpenSCAD source, as an alternative to `nodes` (supply exactly one). Interpreted by the same engine the editor’s .scad import uses; BOSL2/MCAD includes resolve. minkowski() and resize() are not supported here — use hull() or offset()."
  4. First observed

TDQS

A4.3/5.0
Behavior4/5

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

Annotations already declare readOnly/idempotent/non-destructive, so the safety profile is covered. The description adds real behavioral context: results are exact for geometry but an estimate for filament/cost, and a two-body count is a diagnostic signal about operands that never touched — a non-obvious interpretation an agent would otherwise miss.

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?

Three sentences, fully front-loaded with the output set first, then the use case, then the diagnostic behavior. Every clause carries information; no restatement of the name or title.

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

Completeness5/5

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

With no output schema, the description must enumerate what comes back, and it does so precisely (six named quantities). It also supplies the estimation caveat on the filament/cost half, which is the main thing an agent could misread as exact.

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

Parameters3/5

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

Schema description coverage is 100%, so the schema already documents scad/nodes/infill/shellMm/materialId/smoothness. The description adds no syntax, defaults or format guidance for any parameter, so the baseline 3 applies.

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?

Names a precise set of computed quantities (volume, surface area, centre of mass, connected-body count, filament estimate and cost) on a specific resource (a model), and asserts exclusivity — 'nothing else reports those'. An agent can tell this apart from evaluate/render/print_check without opening the schema.

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?

Gives concrete triggering questions ('how heavy / how much material / how much filament / how much will this cost') and a negative boundary ('cannot be derived from a bounding box'). It stops short of naming the sibling to use instead for interference or printability questions, so the routing is clear but not exhaustive.

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

All OwlCAD toolsInspect
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