---
title: "Options-implied probability ladder for BTC/ETH (Deribit) — $0.02/call"
method: GET
path: "/api/v1/implied-prob/{asset}"
tags: ["options", "prediction-markets", "paid"]
---

# Options-implied probability ladder for BTC/ETH (Deribit) — $0.02/call

`GET /api/v1/implied-prob/{asset}`

## Request

- Base URL: `https://kronossignals.com` (the document declares no server; this is the origin it was published from)
- URL: `https://kronossignals.com/api/v1/implied-prob/{asset}`
- Auth: none declared

Returns the options market's probability that BTC or ETH is above each of up to 25 prices at a target time, backed out of the Deribit option book: a skew-inclusive call-spread digital on the mark-IV smile, with total variance interpolated in time between listed expiries. It is the fair value of a prediction-market crypto threshold contract (Kalshi, Polymarket) — compare probability_above with the contract's YES price. Risk-neutral, not a forecast. Malformed input is refused with a free 400 before any payment. $0.02 USDC on Base mainnet via x402. BTC and ETH only.

## Path parameters

- `asset` 'btc' | 'eth', required

## Query parameters

- `strikes` string
- `at` string

## Response `200`

Probability ladder returned (payment verified)

- object
  - `available` boolean
  - `asset` string
  - `target_time` string, date-time
  - `hours_to_target` number
  - `index_price` number, nullable
  - `forward_at_target` number
  - `ladder` object[]
    - `strike` number
    - `probability_above` number
    - `probability_below` number
    - `iv_at_strike_pct` number
    - `extrapolated` boolean
  - `warning` string
  - `expiries_used` object[]
  - `defaults_applied` object
  - `how_to_use` string
  - `method` string
  - `limitations` string[]
  - `source` string
  - `as_of` string, date-time
  - `cache_ttl_sec` integer
  - `disclaimer` string

## Other responses

- `400`: Malformed request (asset, strikes or target time) — refused before payment, nothing charged.
- `402`: Payment Required — x402 micropayment instructions in response body.
- `409`: Payment nonce already used (replay rejected).
- `422`: Target after the last listed Deribit expiry, or a strike more than 5x from the forward — not charged.
- `503`: Deribit option book unreachable — not charged.

---

[API](https://skmtc.dev/kronossignals/apis/kronos-crypto-data-api.md) · [All operations](https://skmtc.dev/kronossignals/apis/kronos-crypto-data-api/llms.txt) · [OpenAPI document](https://skmtc.dev/kronossignals/apis/kronos-crypto-data-api/revisions/bfdcf7230e93?raw)