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Jakeschincariol/trader-skill

>- The Reverse Engineer. Reads a famous investor's public SEC filings (the quarterly 13F-HR, plus Form 4 if you want the insider trades) and rebuilds their portfolio as weights you can copy: every position, its share of the fund, what they bought, added, trimmed and sold since the last quarter, with tickers matched to every CUSIP. Then it writes trader/targets.json so the budget skill can size it to your money. Use when the user says "copy Buffett", "copy Berkshire", "what does Ackman own", "reverse engineer this investor", "show me their 13F", "what did they buy last quarter", "copy the top 5", or names any fund or famous investor.

What is trader-skill?

trader-skill is a Claude Code agent skill that >- The Reverse Engineer. Reads a famous investor's public SEC filings (the quarterly 13F-HR, plus Form 4 if you want the insider trades) and rebuilds their portfolio as weights you can copy: every position, its share of the fund, what they bought, added, trimmed and sold since the last quarter, with tickers matched to every CUSIP. Then it writes trader/targets.json so the budget skill can size it to your money. Use when the user says "copy Buffett", "copy Berkshire", "what does Ackman own", "reverse engineer this investor", "show me their 13F", "what did they buy last quarter", "copy the top 5", or names any fund or famous investor.

Works with✓Claude Code~Codex CLI~Cursor
npx skills add https://github.com/Jakeschincariol/trader-skill/tree/HEAD/trader-copycat
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Documentation

trader-copycat

Copying an investor starts with what they are legally required to show: a 13F-HR, filed with the SEC every quarter by any investment manager with over $100 million in US-listed stocks and other 13(f) securities. This skill reads it straight from SEC EDGAR, rebuilds the portfolio, and turns it into target weights for your own account.

Tool in this folder (standard library Python, no keys):

python3 "${CLAUDE_SKILL_DIR}/edgar13f.py" --help

SEC asks every program to identify itself with a name and email. Set it once in trader/config.json ("sec_user_agent": "Your Name [email protected]", with the user's real name and email) or export SEC_USER_AGENT=.... The tool refuses to call SEC without it and says how to fix it. Ask the user for it; never invent one.

What it writes

  • trader/targets.json: the weights to copy, in the shape every other trader skill reads: { "source", "as_of", "weights": [ {"ticker", "name", "weight"} ] }, weights in % with 2 decimals summing to 100 over the stock sleeve (keep the 2 decimals: budget sizing needs them), plus the 13F share, value, CUSIPs, what was skipped and why, and the caveats.
  • trader/tickers.json (optional, yours): CUSIP to ticker fixes the tool will always use first, as {"650111107": "NYT"}.

targets.example.json in this folder is the real output of the reel's run (Berkshire, top 5).

The rules

  • Say how old the data is, every time. A 13F is a snapshot of the last day of the quarter, filed up to 45 days later. Say "holdings as of 2026-06-30, filed 2026-08-14" in every answer that uses one.
  • Say what it cannot show. Long US-listed positions only: no shorts, no cash, no bonds, no foreign shares, no private companies, nothing bought and sold inside the quarter, and no prices paid.
  • The firm, not the person. Berkshire Hathaway files the 13F, not Warren Buffett. Greg Abel has been CEO since 2026-01-01 and Buffett became Chairman Emeritus on 2026-09-18. Never say "Buffett bought" when the filing only says "Berkshire held".
  • Every number comes from the filing. Quote the accession number and link the information table. If a ticker is a guess (marked *), say so and fix it with --figi or trader/tickers.json before anything is copied.
  • Options and bonds are never copied. PUT, CALL and PRN rows are listed as excluded. This pack trades stocks only unless the config allows more.

Step 1: find the investor

python3 "${CLAUDE_SKILL_DIR}/edgar13f.py" find buffett
python3 "${CLAUDE_SKILL_DIR}/edgar13f.py" find "pershing square" --sec

filers.json lists 23 well-known filers with CIKs checked against SEC on 2026-10-13 (Berkshire, Pershing Square, Scion, Bridgewater, ARK, Duquesne, Appaloosa, Baupost and more). --sec searches every EDGAR filer by name. If a filer has stopped filing (Scion's last 13F-HR was 2025-11-03), say so.

Step 2: read the latest quarter

python3 "${CLAUDE_SKILL_DIR}/edgar13f.py" filings 1067983
python3 "${CLAUDE_SKILL_DIR}/edgar13f.py" holdings 1067983 --combine --top 15

It downloads the submissions list, picks the newest original 13F-HR, finds the information table XML in the filing folder, sums the rows each holding is split into (Berkshire reports one stock across several subsidiaries), checks the total against the cover page, and matches tickers: your trader/tickers.json first, then share_classes.json (verified CUSIPs for companies with several listed classes), then SEC's company_tickers.json by name, and OpenFIGI's free CUSIP lookup with --figi. --combine adds share classes of one company together (Alphabet A + C). If an amendment exists for the quarter, the tool says so; read it with --accession.

Step 3: what changed

python3 "${CLAUDE_SKILL_DIR}/edgar13f.py" diff 1067983

New positions, positions sold out, added and trimmed, by share count against the quarter before. Share counts at two dates, not trades: say "held more shares at June 30 than at March 31", never "bought on" a day.

Step 4: write the targets

python3 "${CLAUDE_SKILL_DIR}/edgar13f.py" copy 1067983 --top 5 --out trader/targets.json

Share classes are combined by default (--separate keeps them apart). --exclude TICKER leaves out what the user will not own, --min-pct 1 drops crumbs. The weights are each position's % of the 13F scaled so the chosen ones sum to 100. Show the table, then hand off to /trader-budget.

Form 4 (optional): insiders and 10% owners report their trades within two business days on Form 4. To see them, open https://www.sec.gov/cgi-bin/browse-edgar?action=getcompany&CIK=<CIK>&type=4&owner=include (or the filer's submissions list) and read the filings the user asks about. They are faster than a 13F but cover one stock at a time.

Example: the reel

"Copy Berkshire Hathaway, top 5." The latest 13F-HR is for the quarter ending 2026-06-30, filed 2026-08-14, accession 0001193125-26-352200, total $299,253,556,246 (matches the cover page).

#holding% of the 13Fcopy weight
1Apple (AAPL)22.0430.67
2American Express (AXP)17.1423.85
3Alphabet (GOOGL + GOOG combined)12.6217.56
4Coca-Cola (KO)10.8615.11
5Bank of America (BAC)9.2012.80

Rounded, that is 30.7 / 23.9 / 17.6 / 15.1 / 12.8. Since the quarter before: new D.R. Horton (3,564 shares), sold out of Constellation Brands, added Alphabet, Delta, Lennar, Macy's and the New York Times, trimmed Bank of America, Kroger, Capital One, Nucor, Ally and DaVita. Then: "These are Berkshire's holdings as of June 30, 2026. Next, /trader-budget sizes them to your $5,000."

What it never does

  • Never claims the investor is still holding today, or why they bought.
  • Never claims returns, or that copying a fund will make money. A 13F copy buys months after the fund did, at today's price.
  • Never places an order. It writes target weights; sizing, risk checks and your yes come after.
  • Never scrapes past SEC's fair-access limits (10 requests a second; the tool stays well under).

Safety

  • Education and tooling, not financial advice. Nothing in this pack is a recommendation to buy or sell anything.
  • Paper trading by default ("paper": true in trader/config.json).
  • Nothing places an order except /trader-broker, and only after /trader-risk passes AND the user types an explicit yes for that order in the chat, AND the brokerage tool is set to "Needs approval" in Claude (Customize > Connectors > tool permissions) so Claude's own "Allow once / Deny" card appears too. Never "Always allow" an order tool.
  • No options, margin, shorting or leverage unless the config allows it and the user confirms.
  • 13F data is quarterly and up to 45 days old when it is filed. Say so.

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