pptx – Documents & Office skill for AI agents

PPTX creation, editing, and analysis

A .pptx is a ZIP archive of XML files. Choose your approach by task:

| Task | Approach |

|---|---|

| Create a new deck | Write a pptxgenjs script — see gotchas below |

| Edit an existing deck, or build from a template | unzip → edit ppt/slides/slideN.xml → zip |

| Read content | markitdown deck.pptx (one block per slide under <!-- Slide number: N --> markers); visual grid: python scripts/thumbnail.py deck.pptx |

Scripts

Paths are relative to this skill's directory. Everything else is plain Python, node, or shell.

| Script | What it does |

|---|---|

| scripts/thumbnail.py deck.pptx [prefix] | Labeled grid of every slide, for picking template layouts. .pptx only. Pass prefix — it defaults to thumbnails, which overwrites the grids of any other deck done in the same directory |

| scripts/add_slide.py unpacked/ slide2.xml [--after slideN.xml] | Duplicate a slide (or a slideLayoutN.xml) with all the package bookkeeping. Also takes a .pptx directly with -o out.pptx |

| scripts/clean.py unpacked/ | Delete slides, media, and rels no longer referenced. Run after <p:sldIdLst> is final |

| scripts/office/validate.py deck.pptx [--original src.pptx] | Schema, relationship, content-type, chart and slide checks; each failure names its fix. Pass --original for any template-derived deck — it baselines the schema checks against the template, so the template's own XSD errors don't read as yours |

| scripts/office/soffice.py --headless --convert-to pdf deck.pptx | LibreOffice wrapper — bare soffice hangs in this sandbox |

Creating with pptxgenjs — gotchas

pptxgenjs is preinstalled — do not run npm install first; write the script and require('pptxgenjs') directly. Only if that require fails: npm install pptxgenjs. The model knows the API; these are the footguns:

• Set pres.layout before adding slides. The default canvas is LAYOUT_16x9 = 10" × 5.625", not 13.3" wide. Coordinates past the edge are written, not clamped — the shape just isn't on the slide. (LAYOUT_WIDE is 13.3" × 7.5".)
• Hex colors: never #, never 8 digits. color: "FF0000". Both "#FF0000" and alpha baked into the hex ("00000020") corrupt the file. For translucency: transparency: 0-100 on fills and images, opacity: 0.0-1.0 on shadows — each is silently ignored on the other.
• pptxgenjs mutates option objects in place (converts values to EMU on first use). Never share one shadow/options object across two add* calls — build a fresh object each time.
• Shadow offset must be ≥ 0 — a negative offset corrupts the file. To cast a shadow upward, use angle: 270 with a positive offset.
• letterSpacing is silently ignored — the real option is charSpacing.
• Lists: bullet: true on each item, never a literal • (renders double bullets). Set breakLine: true on every array item except the last. Space bulleted paragraphs with paraSpaceAfter, not lineSpacing (huge gaps).
• One new pptxgen() per output file — never reuse an instance.
• rectRadius only works on ROUNDED_RECTANGLE, not RECTANGLE.
• Gradient fills aren't supported — use a gradient image as the background instead.
• Text boxes have built-in internal padding — set margin: 0 whenever text must align with a shape, line, or icon at the same x.
• Speaker notes go in slide.addNotes("...") (plain text, once per slide), never in a text box on the slide.
• Keep charts native. Use addChart() for everything PowerPoint can chart (pass an array of {type, data, options} for combos). For PowerPoint-native features the library doesn't expose (trendlines, error bars), compute the extra series yourself or post-process the generated OOXML — do not fall back to a rendered image. Only chart types PowerPoint has no native form for (Sankey, network, chord) go in as images.
• Default charts render bare — no title, no data labels, dated palette. Set showTitle + title, showValue: true + dataLabelPosition, chartColors: [...] from your palette, and quiet the frame (catAxisLabelColor/valAxisLabelColor, valGridLine: { color, size }, catGridLine: { style: "none" }, showLegend: false for a single series).
• On a stacked bar or column chart, dataLabelPosition must be ctr, inEnd, or inBase. outEnd corrupts the file.
• A combo series using secondaryValAxis/secondaryCatAxis needs both valAxes and catAxes on the chart options, two entries each. Without them pptxgenjs writes axis *ids* it never declares, and PowerPoint discards that chart and reports the file as corrupt. Supplying only valAxes is not enough.
• After writeFile(), run python scripts/office/validate.py deck.pptx. It reports the two chart faults above and the slide-XML defects PowerPoint refuses, and names the fix for each. Fix them in your generator, not by hand-editing the packed XML.
• Never reorder the children of <p:presentation>. pptxgenjs writes <p:notesMasterIdLst> right after <p:sldIdLst> and points both masters at one theme part. PowerPoint reads that happily — move the element and the same deck becomes unopenable.
• Icons: render react-icons to SVG (ReactDOMServer.renderToStaticMarkup), rasterize with sharp at ≥256px, and insert via addImage({ data: "image/png;base64," + buf.toString("base64") }) — the image/png;base64, prefix is required (react-icons, react, react-dom, and sharp are preinstalled — npm install react-icons react react-dom sharp only if a require fails).

Editing existing decks and templates

Pick layouts first: python scripts/thumbnail.py template.pptx template-thumbs writes a labeled grid of every slide and prints the file(s) it created — template-thumbs.jpg, split into template-thumbs-N.jpg past 12 slides. Always pass that second argument, named after the deck. It defaults to thumbnails, so two decks thumbnailed in one directory silently overwrite each other's grids — the first deck's are simply gone (template analysis only — visual QA needs the full-resolution renders from [Converting to Images](#converting-to-images); it only accepts .pptx, so copy a .potx to a .pptx name first). Use it with markitdown to map each content section onto a template slide, and vary the layouts — don't put every section on the same title-and-bullets slide.

python3 -c "import sys,zipfile; zipfile.ZipFile(sys.argv[1]).extractall('unpacked')" deck.pptx
python scripts/add_slide.py unpacked/ slide2.xml --after slide2.xml   # duplicate a slide (or slideLayoutN.xml); prints the new slide's path
# reorder / delete slides = edit <p:sldIdLst> in ppt/presentation.xml
python scripts/clean.py unpacked/                                     # after deletions: removes orphaned slides, media, rels
# edit slide content in ppt/slides/slideN.xml
(cd unpacked && rm -f ../out.pptx && zip -Xr ../out.pptx .)           # zip from INSIDE the dir; rm first or deleted parts survive
python scripts/office/validate.py out.pptx --original deck.pptx

• Do all structural work — add, delete, reorder — before editing any slide's content. add_slide.py copies a slide file verbatim, so duplicating after you edit clones the edited content; and clean.py deletes any slide missing from <p:sldIdLst>, including one you just wrote.
• Never copy a slide file by hand — add_slide.py does every registration a new slide needs and reports what it made (Created ppt/slides/slide17.xml from slide2.xml). It also works directly on a file: add_slide.py deck.pptx slide2.xml -o out.pptx — pass -o, or it rewrites the input deck in place. A duplicated slide still *references* its source's chart/SmartArt/embedded-object parts rather than cloning them, so editing one slide's chart changes the other's.
• If you use python-pptx, three things it won't do: duplicate a slide (its only entry point is add_slide(layout)), preserve formatting through text_frame.text = "..." (that collapses the paragraph to a single unstyled run — assign run.text instead), or read the SVG/EMF most template art uses (add_picture raises UnidentifiedImageError).
• Legacy .ppt must be converted first: python scripts/office/soffice.py --headless --convert-to pptx file.ppt. .potx templates unpack and pack identically — keep the .potx extension on the output.
• To reuse a template icon or image, duplicate a slide or layout that already contains it.

When filling in a template:

• If you script an XML transform, parse with defusedxml.minidom — round-tripping OOXML through xml.etree.ElementTree rewrites namespace prefixes and corrupts the deck.
• Template slots ≠ source items. If the template shows 4 team members and you have 3, delete the 4th member's entire group (image + text boxes), not just its text — then check for orphaned visuals in QA.
• One <a:p> per list item — never concatenat

… (full content is in the download package)