Describe

pc:describe

Produce a text description of an existing PartCAD shape by rendering it and looking at the result — the replacement for PartCAD's retired built-in AI summary. The text after the command ($ARGUMENTS) names the object to describe (optionally with its kind).

One picture is not enough to describe a shape. A single projection hides everything behind it, and a description written from one is a description of a silhouette. Render three views (§2), and where a dimensioned drawing can be had, read the numbers off that rather than estimating them (§3).

1. Resolve the object

$ARGUMENTS is the object name (a part by default; an assembly or sketch if the user says so). Read its desc:/requirements: from partcad.yaml for context. Make sure PartCAD is available as /pc:init describes.

Pass --no-ansi on every run so the output is plain text; it is a global flag, goes before the subcommand, and routes the logs to stderr.

This skill describes an object a package declares, because §5 stores the result back into that package. To describe a bare CAD file that is in no package, render it with /pc:render (pc adhoc render) and write the description for the user instead of storing it.

2. Render three views

front, top and iso: two orthographic views to read proportion and features from, and one pictorial view that shows how they go together. A rendered file is named after the object, so give each view a directory of its own or they overwrite each other:

for view in front top iso; do
  mkdir -p /tmp/pc-render/$view
  pc --no-ansi render -t png --view $view -O /tmp/pc-render/$view <name>   # add -a for an assembly
done

View all three — /tmp/pc-render/<view>/<name>.png.

Add right (or back, left, bottom) when the three leave a face unaccounted for: a part that is not symmetric about an axis has a side you have not seen, and guessing at it is exactly what this skill must not do.

A sketch is flat, so it has only one view worth rendering, and SVG suits it better than PNG:

mkdir -p /tmp/pc-render
pc --no-ansi render -s -t svg -O /tmp/pc-render <name>

3. Render a dimensioned drawing (parts, when it is available)

The projections above show shape but no numbers. draftwright, a render implementation published in the public PartCAD index, draws a fully dimensioned technical drawing instead — orthographic views with dimension lines, hole callouts, radii, an ISO view, and a title block carrying the material and scale. Reading a description off that beats estimating from pixels:

mkdir -p /tmp/pc-render/drawing
pc --no-ansi render -t pdf -e //pub/feature/render/draftwright \
    -O /tmp/pc-render/drawing <name>

-e names the package to read the output configuration from, so this works on any object without that object's package knowing about draftwright. Then read /tmp/pc-render/drawing/<name>.pdf — ask for pdf, whose pages can be looked at directly. Its svg draws every character as paths, so no text can be read out of that markup.

This is a best-effort extra, not a requirement. It needs the public index among the package's dependencies: (which pc init writes) and a network connection, and the first run is slow while PartCAD installs draftwright into a sandbox. It is also a part drawing — do not expect it of an assembly or a sketch.

draftwright reports what it could not do. When a part has features it cannot dimension at the chosen scale it says so and draws the rest, and the command may exit non-zero having still written a usable file — so check whether the file appeared before giving up on it. If it did not, or anything above failed, describe the object from the three views and say in your report that no dimensioned drawing was available.

4. Write the description

From the images plus the configured desc/requirements, write a description for a reader who has a mechanical-engineering / CAD background but cannot see it:

• Describe both the overall shape and the dimensions; make no assumptions and add as much concrete detail as the renders and config support.
• Prefer a dimension the drawing states over one you judged from a projection. Where you are reading a proportion off a picture rather than a stated number, say it is approximate rather than inventing a figure.
• Work through the views: overall form and bounding size first, then the features each view reveals, then how they relate.
• Refer to it as "this design", not "the image" — and never as "the three images", which is an artifact of how you looked at it.
• Produce prose that is ready to be narrated as-is (no markdown, no lists).

5. Persist it (so pc inspect shows it)

pc inspect reads a shape's summary: from its configuration. Write your description there so the tool and other agents can reuse it:

parts:            # or sketches: / assemblies:
  <name>:
    ...
    summary: >-
      <your description>

Report the description to the user, say which views (and whether a dimensioned drawing) it was written from, and confirm where you stored it.