monte-carlo

Simulates binary contract probabilities using GBM path sampling and Brier score calibration.

Updated Feb 16, 2026
One-click install
npx skills add https://github.com/travis-burmaster/agentbox --skill monte-carlo-travis-burmaster
Or copy as Structured Prompt for Agent
Please help me install this Agent Skill.
Skill: monte-carlo
Source: https://github.com/travis-burmaster/agentbox/tree/main/examples/llm-proxy-gitagent/workspace/skills/monte-carlo
Command: npx skills add https://github.com/travis-burmaster/agentbox --skill monte-carlo-travis-burmaster

SYSTEM DOCUMENTATION & REQUIREMENTS

💡 This Skill requires numpy.

What problem does it solve? Estimating the probability of binary events like "Will AAPL close above $200?" requires rigorous statistical simulation rather than guesswork. This Skill provides the foundational Monte Carlo methods for pricing binary contracts, quantifying estimation uncertainty with confidence intervals, and measuring forecast calibration. ## Core Features & Use Cases - GBM Path Simulation: Simulates terminal asset prices under Geometric Brownian Motion to estimate binary payoff probabilities with standard errors and 95% confidence intervals. - Sample Size Planning: Computes required path counts for target precision using CLT convergence rates, accounting for maximum variance at p = 0.5. - Brier Score Calibration: Evaluates forecast quality against benchmarks (below 0.20 good, below 0.10 excellent) to compare model sharpness. - Use Case: A prediction market analyst wants to price a contract on AAPL exceeding $200 in 30 days. Provide current price, drift, volatility, and time to expiry to get a probability estimate with confidence bounds. ## Quick Start Ask the agent to simulate the probability of AAPL closing above $200 in 30 days given 20% volatility and 8% drift using Monte Carlo simulation.

Frequently Asked Questions about monte-carlo

High-intent search queries and answers about installing and using this skill.

FAQPage Schema
How do I estimate the probability of a stock exceeding a price target?

Simulate terminal prices under Geometric Brownian Motion using current price, drift, volatility, and time to expiry, then compute the fraction of paths exceeding the strike. The sample mean of indicator payoffs gives the probability estimate with a calculable standard error.

How many Monte Carlo samples do I need for accurate probability estimates?

Sample size depends on target precision and the true probability. For +/-0.01 precision at 95% confidence when p = 0.5 (worst case variance), you need 9,604 samples, derived from N = (1.96)^2 * 0.25 / (0.01)^2.

What is a good Brier score for probability forecasts?

A Brier score below 0.20 is considered good and below 0.10 is excellent. Top election forecasters like FiveThirtyEight and The Economist achieve 0.06-0.12 on presidential races, while always predicting 0.5 yields 0.25.

When does GBM-based Monte Carlo simulation fail?

GBM assumes lognormal returns, constant volatility, and continuous trading, which break down with fat tails, jumps, stochastic volatility, and discrete order books. In these cases, escalate to importance sampling, particle filters, Heston models, or agent-based simulation.

Why is variance highest when the probability is 0.5?

The estimator variance is p(1-p)/N, which is maximized at p = 0.5. This means the most uncertain binary contracts require the most simulation paths to achieve a given precision level.