The filing

Every institutional investment manager running over $100M in U.S. equities has to file a Form 13F with the SEC. Quarterly. Within 45 days of quarter end. It lists every long position in publicly traded stocks, with share count and market value as of the last trading day of the quarter.

That's a lot of paper. EDGAR publishes thousands of these each cycle. They're public, free, and roughly machine-readable if you enjoy parsing 1990s-vintage XML.

Most people don't. So if you're an agent trying to figure out what Renaissance bought last quarter, you've got two options. Either you parse the filings yourself (and re-parse when EDGAR's schema drifts, which it does), or you pay someone else. Bloomberg charges $24k/seat/year. WhaleWisdom charges $300/year for a screen-scrapable web UI. Both are priced for humans.

What the endpoint does

13f-deltas reads two consecutive 13Fs for the same CIK and returns the diff. New positions. Closed positions. Position size changes (share count delta and percent change). Value movement quarter over quarter. 

curl "https://api.agentutility.dev/edge-finance/13f-deltas?cik=0001067983&quarter=2025Q4"

0001067983 is Berkshire Hathaway. The response comes back JSON, not XML, with one entry per ticker that moved. 

{
  "cik": "0001067983",
  "filer": "Berkshire Hathaway Inc",
  "quarter": "2025Q4",
  "filed_at": "2026-02-14",
  "previous_quarter": "2025Q3",
  "deltas": [
    {
      "ticker": "AAPL",
      "cusip": "037833100",
      "action": "reduced",
      "shares_prev": 300000000,
      "shares_curr": 280000000,
      "shares_delta": -20000000,
      "pct_change": -6.67,
      "value_curr_usd": 65800000000
    },
    {
      "ticker": "OXY",
      "action": "increased",
      "shares_delta": 8500000,
      "pct_change": 3.4
    }
  ]
}

Pull the live response for actual figures. The shape above is what you'll get back.

Berkshire's Apple trim

Buffett's Apple position has been the story for six quarters running. Berkshire went from ~915M AAPL shares at end of 2023 to roughly 300M by mid-2025, parking the proceeds in T-bills. That trim showed up in 13f-deltas as the largest single-position dollar move in U.S. markets, quarter after quarter, until it finally stopped.

A research agent watching cik=0001067983 and surfacing changes above $1B in market value would have flagged each cut the day the filing dropped. No PDF parsing. No "we'll get back to you next quarter when our analyst writes the note."

Pricing math

Each call is $0.005 USDC, settled via x402 on Base through CDP at 0x8f5cb67b49555e614892b7233cfddebfb746e531.

An equity-research agent screening 100 funds a week pays $0.50. A weekly. The same coverage from a commercial vendor is two to three orders of magnitude more, and you can't point an LLM at it without breaking the ToS.

If you're running a fund-of-funds attribution model that hits every 13F filer above $1B AUM (roughly 2,800 of them) once a quarter, the bill is $14 for the entire universe. The cost-of-data line item disappears from your P&L.

What it doesn't do

Short positions, swaps, and options-as-puts don't show up in 13F. Funds report only long equity. If you're tracking sentiment, this is one ingredient. If you want to know what Pershing Square is short, you need 13D/G filings (different endpoint, on the way).

13f-deltas also won't backfill. Two consecutive quarters per call. For a longer time series, loop the endpoint per quarter pair and stitch the JSON client-side. Still cents.

Calling it

Full schema lives at agentutility.ai/clusters/edge-finance/13f-deltas. The MCP-tool wrapper is in the same listing. If you're routing through Coinbase's x402 directory, search "13F" and pick the one priced at half a cent.