Expected Value Calculator

Calculate expected value for any sports bet or prediction market position. Supports American odds, decimal odds, implied probability, and Kalshi contract pri...

Security Scan

The skill is internally consistent: it only requires python3 and its SKILL.md contains a small local Python one-liner to compute EV from supplied odds and a probability — nothing requested or instructed appears out of scope for an EV calculator.

Purpose & Capability

Name/description, required binary (python3), and runtime instructions all align with computing expected value for bets and prediction-market positions. No unrelated credentials, binaries, or config paths are requested.

Instruction Scope

Runtime instructions are an inline python3 command that reads two command-line arguments (odds and estimated probability) and prints EV, edge, and a verdict. The instructions do not access files, environment secrets, or network endpoints. Minor implementation caveats: the script's input parsing is simplistic (e.g., percent detection uses a >1 numeric check, limited handling of formats like '40%' or other variants), which may misinterpret some inputs but is not a security issue.

Install Mechanism

No install spec; instruction-only skill. This minimizes disk writes and supply-chain risk. The only runtime requirement is python3 being available on PATH.

Credentials

No environment variables, credentials, or config paths are requested. The declared requirements match what the skill does.

Persistence & Privilege

always:false and user-invocable:true (defaults). The skill does not request persistent or elevated privileges and does not modify system or other-skill configuration.

Assessment

This skill appears coherent and low-risk: it runs a local python3 one-liner using only the odds and probability you pass in and does not send data elsewhere. Before installing, verify you trust the skill source (registry owner) and that python3 on the host is the expected interpreter. Be aware the script uses simple parsing and may mis-handle some input formats (e.g., '40%' or unusual odds strings); if you need broader input support or stricter validation, request an updated SKILL.md or a version that runs a small packaged script with explicit input validation. If you want extra caution, run the single python command locally yourself to confirm its behavior before enabling the skill for automated use.

Calculate the expected value of any bet given offered odds and your estimated true probability.

When to Use

Use this skill when the user asks about:

• Expected value of a bet
• Whether a bet is +EV or -EV
• Is this bet worth taking at these odds
• Breakeven probability for given odds
• Comparing EV across multiple bets
• Finding the best value bets on a slate
• How much edge they have on a line

Odds Conversion Reference

Before computing EV, convert all inputs to decimal odds:

Format	Example	To Decimal Odds
American (+)	+150	1 + odds/100 = 2.50
American (-)	-200	1 + 100/
Decimal	2.50	Already decimal
Implied Prob	40%	1/prob = 2.50
Kalshi price	$0.40	1/price = 2.50

Operations

1. Single Bet EV

Calculate expected value for one bet. User must provide: odds (any format) and their estimated true probability.

python3 -c "
import sys

odds_input = sys.argv[1]
true_prob = float(sys.argv[2]) / 100 if float(sys.argv[2]) > 1 else float(sys.argv[2])

# Convert to decimal odds
if odds_input.startswith('+'):
    decimal_odds = 1 + int(odds_input) / 100
elif odds_input.startswith('-'):
    decimal_odds = 1 + 100 / abs(int(odds_input))
elif odds_input.startswith('$') or odds_input.startswith('0.'):
    price = float(odds_input.replace('$', ''))
    decimal_odds = 1 / price
else:
    decimal_odds = float(odds_input)

implied_prob = 1 / decimal_odds
ev_per_dollar = true_prob * decimal_odds - 1
edge = true_prob - implied_prob

print(f'Offered odds: {odds_input} (decimal {decimal_odds:.3f})')
print(f'Implied probability: {implied_prob:.1%}')
print(f'Your true probability: {true_prob:.1%}')
print(f'Edge: {edge:+.1%}')
print(f'EV per \$1: {ev_per_dollar:+.4f}')
print(f'EV per \$100: {ev_per_dollar * 100:+.2f}')
print(f'Verdict: {\"✅ +EV — BET\" if ev_per_dollar > 0 else \"❌ -EV — PASS\"} ')
" "ODDS" "TRUE_PROB_PERCENT"

## About

Built by [AgentBets](https://agentbets.ai) — full tutorial at [agentbets.ai/guides/openclaw-ev-calculator-skill/](https://agentbets.ai/guides/openclaw-ev-calculator-skill/).

Part of the [OpenClaw Skills series](https://agentbets.ai/guides/#openclaw-skills) for the [Agent Betting Stack](https://agentbets.ai/guides/agent-betting-stack/).