skill
third-sphere-portfolio-company-skills-public
Claude skills we've developed or refined for Third Sphere portfolio companies.
Set up
Skills are installed by placing their folder where your agent loads skills.
The download comes from github.com/third-sphere/third-sphere-portfolio-company-skills-public itself, not from our server, so what you get is exactly what its author published.
Install instructions come from the README
README
synced Oct 27, 2026Third Sphere Portfolio Company Skills
A curated collection of Claude Code skills built and shared by Third Sphere with our portfolio companies.
Installation
The same marketplace works everywhere Claude supports plugins — Claude Code, Cowork, and chat on claude.ai or the desktop app. Nothing to download first, and no GitHub account needed: the repo is public.
Marketplace: https://github.com/third-sphere/third-sphere-portfolio-company-skills-public
Claude Code
Two commands, from inside a session:
/plugin marketplace add third-sphere/third-sphere-portfolio-company-skills-public
/plugin install portco-skills@third-sphere
If the install summary says Run /reload-plugins to activate, run that. Claude
Code clones the marketplace, so git needs to be on your PATH — it almost
certainly already is.
Skills are namespaced by the plugin: /portco-skills:pitch-content-guide. Add
--scope project to the install to share it with everyone on a repo via
.claude/settings.json.
Cowork
Customize in the sidebar → Plugins → Add marketplace → paste the repo
URL (or the owner/repo shorthand) → install Third Sphere Portfolio Company
Skills. Click Update on the marketplace later to pull new versions.
claude.ai and the Claude desktop app (chat)
Requires a paid plan (Pro, Max, Team, or Enterprise).
Customize in the left sidebar → Plugins tab → under Personal plugins click + → Add marketplace → Add from a repository → paste the repo URL. Then Browse plugins and Install.
Installed skills show up via / or the + button in a conversation.
Note that hooks and subagents only run in Cowork and Claude Code. This plugin ships neither, so nothing is lost in chat.
Copying the folders by hand
Use this if you want only some of the skills, or want to edit them locally without forking.
git clone https://github.com/third-sphere/third-sphere-portfolio-company-skills-public.git
cp -r third-sphere-portfolio-company-skills-public/skills/* ~/.claude/skills/
Then restart Claude Code. Copied this way the skills are not namespaced, so they
invoke as /seed-pitch-kit rather than /portco-skills:seed-pitch-kit.
For claude.ai without a paid plan, individual skills can be uploaded one at a
time under Customize → Skills → + → Upload a skill, as a .zip whose root is
the skill folder itself. Code execution must be enabled in Settings →
Capabilities. The plugin route above is easier where it is available.
What needs what
Most of these skills are instructions and work anywhere. Five caveats:
| Skill | Needs |
|---|---|
archive-trailer | ffmpeg, Python with numpy and Pillow, and network access to movingimagearchive.com and Wikimedia Commons. Use it in Claude Code or anywhere with code execution; clip-selection pages also need the separate visual-review skill. |
visual-review | Python with Pillow; ffmpeg for video options; optional playwright for the pre-publish browser check. Pages embed their images, so it works where remote images are blocked. |
portco-brand-extract | Browser tools to read computed CSS, plus network access for the asset crawl. Use it in Claude Code; it degrades badly where Claude cannot reach the live site. |
road-audio-brief | Audio mode only: Python with kokoro-onnx and soundfile, ffmpeg for MP3, and a one-time ~350 MB model download from GitHub. Text and Gemini-script modes work anywhere. |
capstackcompass-public-portco-skill | Network access to reach the CapStack Compass database. |
Available skills
| Skill | What it does |
|---|---|
| archive-trailer | Cut a movie-trailer-style promo (60 s, plus 30 s and 15 s cutdowns) entirely from public-domain archival footage — script beats, clip search and screening, face-aware framing, cards timed for slow readers, synthesized trailer hits, a public-domain music edit, -14 LUFS mix, and tests that catch the failures that cost a round |
| visual-review | Build an interactive page for choosing between visual options across many items (clips, photos, design variants), with open decisions, autosave and a JSON export pasted back into chat; merges rounds without losing earlier answers |
| better-writing | Diagnose and strengthen narrative structure in drafts (stories, essays, posts) — finds where writing takes default, low-risk choices and proposes concrete structural revisions |
| capstackcompass-public-portco-skill | Look up climate credit and non-dilutive capital providers in the CapStack Compass database (capstackcompass.ai), and suggest new providers or corrections through Third Sphere's review queue |
| founder-update | Build portfolio company investor updates (weekly/monthly) with OKRs, metrics dashboards, and trend charts — pulls data from CRM, billing, and finance tools to create polished, data-driven founder letters |
| model-router | Choose the model, surface, and effort for a unit of work in Claude or Codex — keeps the current executor unless task evidence, capability, quota, or total cost justifies a switch, and carries acceptance checks and an escalation trigger across any change |
| pitch-content-guide | Write a slide-by-slide content spec for a fundraise deck — verbatim copy, chart specs, named image assets, review flags, and a pressure test — then emit the ready-to-paste prompt for the design session that builds it |
| portco-brand-extract | Reverse-engineer a company's visual identity from its live website into a measured style guide, a categorised image-asset library, and a browsable brand board |
| road-audio-brief | Turn articles, forum threads, transcripts and notes into spoken briefs for listening while driving — editorial digests written for the ear, full cleaned readouts, local MP3s via free offline Kokoro neural TTS, or paste-ready segmented scripts for the Gemini TTS Playground |
| seed-pitch-kit | Generate complete seed-stage fundraising materials — investment memo, TEA & market sizing, financial model, pitch decks, outreach emails, and investor list — all built comprehensive-to-concise from a shared narrative foundation |
| startup-deck-generator | Tailor a pitch deck for one named target investor — research the fund, diff the deck against what they need, build the tailored HTML version from a brandable shell, and write the approach and objection strategy |
| tufte-viz | Design and critique data visualizations using Edward Tufte's principles — data-ink ratio, chartjunk elimination, graphical integrity, small multiples, and sparklines for honest, high-density charts in decks, updates, and dashboards |
Making it yours
The skills are deliberately plain markdown, so adapting them to your company is editing prose, not writing code.
Try before installing. Point Claude Code at a local clone for one session:
claude --plugin-dir ./third-sphere-portfolio-company-skills-public
Fork and re-point. Fork this repo, edit the skills, and add your fork as the
marketplace instead. Your team installs from yours, and you can still pull our
changes with a normal git merge upstream/main:
claude plugin marketplace add your-org/your-fork
Override one skill locally. A skill you copy into ~/.claude/skills/ sits
alongside the plugin copy rather than replacing it — plugin skills are namespaced,
so /my-version and /portco-skills:their-version both exist. Edit freely without
losing the original.
Validate before you distribute a fork:
claude plugin validate .
What is a skill?
A skill extends Claude Code with a focused capability you can invoke by typing /<skill-name> or a trigger phrase.
Anatomy of a skill
SKILL.md— the core workflow and instructionsREADME.md— design notes, changelog, and usage examplesreferences/,scripts/,assets/— supporting files (optional)
Every skill here lives in exactly one place, skills/<name>/, and is served both
ways from there — the plugin manifest in .claude-plugin/ points at this repo
root, so adding a skill to skills/ ships it through both install paths at once.
Learn more: Claude Code documentation
License
Mozilla Public License 2.0. In practical terms:
- Use it however you like, including commercially. No permission needed, no fee, no requirement to be a Third Sphere portfolio company.
- Internal use carries no obligations at all. Fork it, rewrite every skill, never tell anyone. The license only engages when you distribute your version.
- If you distribute a modified skill, that file stays open. Publish your changed files under the MPL so the next person gets what you got. This is file-level copyleft: you can combine these skills with proprietary work, and only the files you changed carry the obligation — not your product.
- Keep the notices. Copyright and license notices travel with the files.
- The trademarks are not included. "Third Sphere" and "CapStack Compass" are ours; MPL section 2.3 grants no rights in them. Name your fork something else.
Contributions are accepted under the same license.
Disclaimer
These skills are provided as-is, without warranty of any kind, as stated in section 6 of the LICENSE. Third Sphere makes no warranty of fitness for any particular purpose. Each skill's behavior depends on Claude's underlying model and capabilities, which may change over time.
Built with Claude.