Equibles is an MCP server that gives ChatGPT and Claude SEC filings and market data. On November 3, 2026, I ran an "are insiders buying?" workflow through it on GameStop, where the CEO bought 4,144,810 shares for $97.2 million between September 10 and October 13. The answer is only useful if three things are handled before the model ever sees the rows.

1. Not every "acquisition" is a purchase

A Form 4 row carries a transaction code. P is an open-market purchase; A is an award, M an option exercise, F shares withheld for tax, G a gift. All of them can raise the insider's share count. If the tool hands the model raw rows, "the CFO acquired 50,000 shares" reads like conviction when it was a grant.

The GetInsiderTransactions tool maps codes to a Type column where only Buy and Sell mean open-market trades, and says so in the tool description. GameStop's 16 trades since August happened to be 12 buys and 4 sales, with no awards in the window, which makes it an easy case.

2. The 10b5-1 box changes what a sale means

Since 2023 the Form 4 has a checkbox for trades made under a Rule 10b5-1 plan, set up months in advance. Three of GameStop's four sales were plan sales by two officers; one sale of 7,297 shares was not. The cluster-buy ranking (GetInsiderSentimentScores) drops plan trades, which is why it reports five buyers and one seller, and net purchases of $99,001,920. Summing the rows myself, buys minus that one unplanned sale came to $99,001,922. A model that counts every sale would report a different story.

Older filings predate the checkbox, so the column needs a third value ("-") rather than a false "No".

3. Splits break price history but not balances

Ryan Cohen's purchase history goes back to December 2020: 1,226,400 shares at $15.51 on average, then March 2022 at $101.76. Both are as filed, before GameStop's four-for-one split in July 2022. Divide by four: the 2020 buys were about $3.88 a share on today's basis, and the 2022 buys about $25.44, close to today's $24.

Prices stay as filed, so a reader can match each one to its filing. The "Owned After" balance, though, is restated onto today's share count and tracked per security and ownership form, so a balance from 2020 lines up with one from 2026. Mixing the two conventions in one column is how an assistant ends up telling you an insider "paid $100 a share" for a $24 stock.

Checking the output

For the October 13 trades, the Form 4 (accession 0000921895-26-002784) shows code P, 67,130 shares at $26.75 and 777,000 at $27.00, 42,492,652 shares owned afterwards, direct ownership, 10b5-1 box unchecked. That matches the tool's rows field for field, and it's the check I'd tell anyone to do on the one trade they care about.

The full walkthrough, six prompts with the answers, is here:

https://equibles.com/blog/how-to-track-insider-buying-with-chatgpt-or-claude

If you've built tools over Form 4 data: do you expose transaction codes to the model, or map them first?

Data: SEC Forms 4 and 144, processed by Equibles.