Where it is
On github.com/ebregolin/order-sizer, free and open source under the Apache 2.0 licence. The code is three Python files you can read in half an hour, and it is published there so that you can read it before installing it. The README says how: you download one file and drag it into a conversation.
What you need
An AI assistant: today the tool works with Claude, in the desktop application. And a broker the assistant can reach. Interactive Brokers is the one that opened that door: you connect your account to your assistant, with your own credentials, and from then on the assistant can see your positions and the prices. I have no relationship with Interactive Brokers and receive nothing from them — I write that because naming a broker usually means the opposite.
What actually changes
Until now those three things have sat apart: the research you read, what the market is doing, and the account you actually hold. Seeing them together took a terminal on the desk, and the kind of job that comes with one.
Now they can sit in the same place, because you are the one putting them there: the research arrives, you connect the account, the assistant reads the prices. And once all three are present, you can ask. What this issue would mean for my portfolio. How it sits with what I already hold. Why the market moved the way it did this morning, and whether that changes anything in the reasoning I have just read. What I am not taking into account.
These are the questions that, in a bank, you put to a desk. Putting them about what you actually hold, at two in the morning, without asking anyone’s permission, is the new part.
Then there is the laborious part: turning a percentage weight into a quantity, with the exchange rate, the contract multiplier, the rounding to a whole contract and a limit price. It is arithmetic, but it is arithmetic that costs you when it is wrong. That is what the tool does.
Why a tool, and not just the assistant
Because a language model is not deterministic: asked the same question twice, it can answer in two different ways. Ninety-nine times out of a hundred that is a difference in wording; on a quantity it is a wrong order. So the model does not do the arithmetic. A piece of code does — one that returns the same result every time from the same figures, and that can do nothing else: no network access, no call to any broker, no opinion. The assistant runs it, reads what it produced and explains it to you. The calculation never passes through the model.
Who decides
You do, and in one place only: the order the tool prepared sits in your own broker’s application, with your finger over it, until you send it yourself. That is not a promise from me, it is a limit imposed by Interactive Brokers, and neither I nor your assistant can get around it.
Which also means the last check is yours. You are reviewing a quantity somebody else computed, on an amount of capital you chose, about a position you read because I published it. If one of those three does not convince you, you do not press.
And one thing should be said as a matter of fact rather than of caution: I am not selling you this combination. I publish research, and that is what you pay for. The assistant is yours, the account is yours, the tool is free and works with any source that publishes an instrument and a weight. I do not manage your portfolio, I give no personal recommendations, and I do not answer questions about your own situation: questions about the research I answer publicly, to everyone at once. What I have done is publish in a format a machine can read, and write the arithmetic.
What it does not do
It does not decide. It does not assess whether a trade suits you, it does not profile you, and it asks you nothing about your circumstances.
It does not send or transmit orders, and it cannot move money.
It sends me nothing. No telemetry of any kind: it cannot tell me that you installed it, that you ran it, or what you did with it.
It does not choose the source, and it passes no judgement on the one you choose.
What it costs
Nothing, and it is not included in the subscription because there is nothing to include: it is free software, and no part of the price of the research pays for it. If you never use it, the research is identical.