nodecode-prediction-markets
PredictionMarketsPicks: EV, Kelly sizing, Bayesian updating, odds conversion, base-rate gaps and combo edge for Kalshi and Polymarket contracts, as six tools the model calls and one command you type. A Nodecode rewrite of predictionmarketspicks/mcp by predictionmarketspicks.
Get it
Tell the agent "add the prediction-markets cell", or run nodecode add nc://prediction-markets.
Use it
Ask a question the numbers answer: "I think this contract is 55% and it trades at 40 cents — what is my edge?", "how much of a $2,000 bankroll is half-Kelly at 45 cents if I put the win probability at 60%?", "what is +150 as a probability?", "is this 2-leg combo worth the price my venue quoted?".
The model calls one of the six tools:
| Tool | What it answers |
|---|---|
calculate_ev |
the edge in percent from a contract's price in cents and your probability, with a BUY / SELL / SKIP read at ±5%. |
kelly_size |
the stake in dollars at full, half, quarter or eighth Kelly, its share of the bankroll and a risk rating. |
bayes_update |
a prior updated by one or more pieces of evidence, with every step and its change. |
convert_probability |
implied probability, American odds and decimal odds, from any one of the three. |
base_rate_gap |
a market price against one of twelve curated historical base rates (or your own): the gap in points, a signal and the sample quality. |
combo_edge |
a same-game combo's fair-value band, and — given the price a venue quoted — its EV and a 7-tier verdict. |
From eval, the same six are functions in the prediction-markets package:
(prediction-markets:calculate-ev :market-price 40 :your-probability 55) (prediction-markets:kelly-size :win-probability 60 :market-price 45 :bankroll 1000 :fraction "half") (prediction-markets:base-rate-gap :market-price 60 :base-rate-id "fed_hold_unemp_below_4")
and /prediction-markets does the same from a line you type:
/prediction-markets ev 40 55 /prediction-markets kelly 60 45 2000 /prediction-markets convert -150 american /prediction-markets base-rate 60 fed_hold_unemp_below_4 /prediction-markets combo 50,45 22 -150 /prediction-markets ids
Two rules the calculators keep, from the original: a probability is a percent (71, not 0.71) and a value between 0 and 1 is refused rather than guessed at, unless you set percent_guard to false; and a combo is graded against the quote a venue gave you, never against the product of its leg prices, which no venue pays on legs that settle together.
Set it up
Nothing is required: the calculators are offline arithmetic on the numbers you pass, with no key and no network. Three settings are optional:
| Setting | Default | What it is |
|---|---|---|
bankroll |
1000 |
the bankroll /prediction-markets kelly sizes against, when the call names none |
default_fraction |
"half" |
the Kelly fraction that command applies when it names none |
percent_guard |
true |
refuse a probability passed as a decimal fraction (0.71) instead of a percent (71) |
What is in it
| File | What it is |
|---|---|
calc.lisp |
the six calculators' arithmetic, ported from the original's src/lib/formulas.js, src/lib/combo-price.js and src/tools.js. |
cell.lisp |
the twelve curated base rates, the six boundary contracts, the six tools, /prediction-markets and the manual. |
package.lisp |
the prediction-markets package and the cell's one condition. |
Every answer is arithmetic on what you supplied: no live price is read, so quote the price you passed along with it.
License
MIT. The calculators and the base rates are Copyright (c) 2026 PredictionMarketsPicks: see LICENSE and NOTICE.
