# FX Z-Score & Mean-Reversion API > How statistically stretched each currency pair is right now versus its own recent average — the z-score mean-reversion gauge — computed live from Yahoo Finance daily rates (no key, nothing stored). A price alone tells you nothing about whether a pair is cheap or dear; the z-score does: it measures how many standard deviations the current rate sits above or below its rolling mean. A pair two standard deviations above its average is statistically overbought and prone to snap back; two below is oversold. The zscore endpoint returns, for a pair, the current rate, its rolling mean and standard deviation, the z-score, the percent distance from the mean and a plain overbought / oversold label. The screener endpoint scans the major and cross pairs and ranks them by how stretched they are — the most overbought and most oversold at a glance, the mean-reversion opportunity scan. The pairs endpoint lists what is covered. The statistical-stretch / mean-reversion cut for FX — distinct from the FX range, pivot-point, volatility and signals APIs. It answers how far from normal a pair is, not where its support sits or how fast it moves. ## Authentication All requests require your oanor API key in the `x-oanor-key` header. Get one at https://www.oanor.com/developer/keys. ```bash curl -H "x-oanor-key: oanor_live_…" "https://api.oanor.com/fxzscore-api/..." ``` ## Pricing - **Free** (Free) — 900 calls/Mo, 2 req/s - **Starter** ($10/Mo) — 22,500 calls/Mo, 6 req/s - **Pro** ($29/Mo) — 110,000 calls/Mo, 18 req/s - **Business** ($71/Mo) — 560,000 calls/Mo, 45 req/s ## Endpoints ### Z-Score #### `GET /v1/zscore` — Z-score, mean, std-dev and overbought/oversold label for one pair **Parameters:** - `pair` (query, required, string) — FX pair (see /v1/pairs) Example: `EURUSD` - `window` (query, optional, string) — Rolling window in trading days (20-250) Example: `100` **Example:** ```bash curl -H "x-oanor-key: $KEY" \ "https://api.oanor.com/fxzscore-api/v1/zscore?pair=EURUSD&window=100" ``` **Response:** ```json { "data": { "base": "EUR", "mean": 1.169, "note": "z_score = (current rate - rolling mean) / rolling standard deviation over window_days. Above +2 is statistically overbought (stretched high, mean-reversion expects a pullback); below -2 is oversold. Sample standard deviation. Not financial advice.", "pair": "EURUSD", "rate": 1.15808, "quote": "USD", "signal": "neutral / fair value", "source": "Yahoo Finance", "std_dev": 0.01254, "z_score": -0.87, "window_low": 1.14351, "window_days": 100, "window_high": 1.20176, "observations": 100, "pct_from_mean": -0.93 }, "meta": { "timestamp": "2026-06-12T10:35:26.417Z", "request_id": "e8479c4b-a8d8-48d6-b651-3171cce3a764" }, "status": "ok", "message": "Z-score retrieved successfully", "success": true } ``` ### Screener #### `GET /v1/screener` — Major/cross pairs ranked by absolute z-score **Parameters:** - `window` (query, optional, string) — Rolling window (20-250) Example: `100` - `pairs` (query, optional, string) — Optional comma list to restrict scan Example: `EURUSD,USDCAD,GBPJPY` **Example:** ```bash curl -H "x-oanor-key: $KEY" \ "https://api.oanor.com/fxzscore-api/v1/screener?window=100&pairs=EURUSD%2CUSDCAD%2CGBPJPY" ``` **Response:** ```json { "data": { "note": "Major and cross FX pairs ranked by absolute z-score (most statistically stretched first). A high positive z-score is overbought (mean-reversion expects a fall); a low negative one is oversold. Use most_stretched for the headline opportunities.", "pairs": [ { "base": "USD", "mean": 1.37257, "pair": "USDCAD", "rate": 1.39825, "quote": "CAD", "signal": "extremely overbought (mean-reversion: likely to fall)", "std_dev": 0.01113, "z_score": 2.31, "window_low": 1.3492, "window_high": 1.39825, "observations": 100, "pct_from_mean": 1.87 }, { "base": "GBP", "mean": 212.59558, "pair": "GBPJPY", "rate": 214.808, "quote": "JPY", "signal": "overbought", "std_dev": 2.00443, "z_score": 1.1, "window_low": 207.728, "window_high": 216.05499, "observations": 100, "pct_from_mean": 1.04 }, { "base": "EUR", "mean": 1.169, "pair": "EURUSD", "rate": 1.15808, "quote": "USD", "signal": "neutral / fair value", "std_d …(truncated, see openapi.json for full schema) ``` ### Pairs #### `GET /v1/pairs` — Supported FX pairs **Example:** ```bash curl -H "x-oanor-key: $KEY" \ "https://api.oanor.com/fxzscore-api/v1/pairs" ``` **Response:** ```json { "data": { "note": "Supported FX pairs (majors and popular crosses). Pass any of these as pair= to /v1/zscore or as a comma list to /v1/screener?pairs=.", "count": 25, "pairs": [ { "base": "EUR", "pair": "EURUSD", "quote": "USD" }, { "base": "GBP", "pair": "GBPUSD", "quote": "USD" }, { "base": "USD", "pair": "USDJPY", "quote": "JPY" }, { "base": "USD", "pair": "USDCHF", "quote": "CHF" }, { "base": "AUD", "pair": "AUDUSD", "quote": "USD" }, { "base": "USD", "pair": "USDCAD", "quote": "CAD" }, { "base": "NZD", "pair": "NZDUSD", "quote": "USD" }, { "base": "EUR", "pair": "EURGBP", "quote": "GBP" }, { "base": "EUR", "pair": "EURJPY", "quote": "JPY" }, { "base": "GBP", "pair": "GBPJPY", "quote": "JPY" }, { "base": "EUR …(truncated, see openapi.json for full schema) ``` ### Meta #### `GET /v1/meta` — Service metadata **Example:** ```bash curl -H "x-oanor-key: $KEY" \ "https://api.oanor.com/fxzscore-api/v1/meta" ``` **Response:** ```json { "data": { "note": "pair is a supported FX pair (EURUSD, GBPJPY, ...; see /v1/pairs). window is 20-250 trading days (default 100). z-score uses the sample mean and standard deviation of the window. Read fresh per call, nothing cached.", "source": "Yahoo Finance daily FX rates, live", "service": "fxzscore-api", "endpoints": { "GET /v1/meta": "This document.", "GET /v1/pairs": "The supported FX pairs.", "GET /v1/zscore": "Z-score, mean, std-dev and overbought/oversold label for one pair (pair=EURUSD, window=100).", "GET /v1/screener": "All major/cross pairs ranked by absolute z-score, with overbought/oversold counts (window=100)." }, "description": "FX z-score & mean-reversion — how statistically stretched each currency pair is versus its rolling average, live from Yahoo Finance (no key, nothing stored). zscore returns a pair's current rate, rolling mean and standard deviation, the z-score, percent from mean and an overbought/oversold label. screener ranks the major and cross pairs by how stretched they are. pairs lists what is covered. The statistical-stretch / mean-reversion cut for FX — distinct from the FX range, pivot-point, volatility and signals APIs. It answers how far from normal a pair is.", "eurusd_z_score": -0.87, "pairs_supported": 25, "upstream_status": "ok" }, "meta": { "timestamp": "2026-06-12T10:35:26.826Z", "r …(truncated, see openapi.json for full schema) ``` --- Marketplace page: https://www.oanor.com/api/fxzscore-api OpenAPI spec: https://www.oanor.com/api/fxzscore-api/openapi.json