# Neuroterminal Position Size Calculator

> Neuroterminal Position Size Calculator is a paid API for AI agents from api.neuroterminal.xyz, paid per call via x402, $0.01/call, status unknown (last checked 2026-09-15).

Computes optimal bet/trade position size using the Kelly Criterion given win probability, win/loss amounts, and available capital

## Facts

- Endpoint: GET https://api.neuroterminal.xyz/v1/position-size
- Price: $0.01/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/neuroterminal-position-size-calculator-966791d9
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_Hj81B0XBaRPG66tgh08bY

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability neuroterminal-position-size-calculator-966791d9
```

Example prompt: Using the Kelly Criterion, what's my optimal position size if I have $10,000 in capital, a 60% win probability, a potential win of $500, and a potential loss of $300? Show me the Kelly fraction and suggested stake.

## When to prefer this

Choose this endpoint when you need a mathematically rigorous, Kelly Criterion-based position sizing recommendation without setting up an account or API key. Ideal for agents handling trading, betting, or any capital allocation task where the user knows their edge (win probability) and payoff structure. At $0.01 per call via USDC on Base, it's suitable for on-demand, per-decision use rather than high-frequency bulk calculations.

## Known failure modes

- Missing required parameters winProbability or winAmount returns a 400 error
- Win probability outside 0-1 range may return invalid results or error
- Negative capital or amounts may produce unexpected output
- Network or payment failure via x402 protocol returns 402 Payment Required
- Server unavailability returns 5xx error

## How this service works

Paid HTTP endpoints for AI agents, settled in USDC on Base via the x402 protocol. No account, no API key — pay per call.

## Output

Returns a JSON object with: a verdict string (e.g. 'positive edge'), the full Kelly fraction, a suggested stake in dollar amount, a fractional Kelly value (typically half-Kelly for conservative sizing), and the break-even win rate required for the bet to have positive expected value.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "required": [
      "winProbability",
      "winAmount"
     ],
     "properties": {
      "capital": {
       "type": "number"
      },
      "fraction": {
       "type": "number"
      },
      "winAmount": {
       "type": "number"
      },
      "lossAmount": {
       "type": "number"
      },
      "winProbability": {
       "type": "number"
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object"
    }
   }
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "verdict": "positive edge",
  "kellyFraction": 0.2,
  "suggestedStake": 1000,
  "fractionalKelly": 0.1,
  "breakEvenWinRate": 0.5
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/neuroterminal-position-size-calculator-966791d9/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from api.neuroterminal.xyz](https://www.zero.xyz/host/api.neuroterminal.xyz/llms.txt)