# Cross-Asset Tail Risk API > Ranks the major markets by how brutal their bad days are, computed live from Yahoo Finance daily closes — no key, nothing stored. Volatility and the Sharpe ratio assume returns are symmetric and well-behaved, but the losses that actually blow up a book live in the left tail — the rare, deep down-days a standard-deviation number smooths away. This API measures that tail directly. For each market it returns Value-at-Risk (the daily loss not exceeded on 95% / 99% of days, both the historical percentile and the normal-distribution parametric estimate), the Conditional VaR / Expected Shortfall (the average loss on the worst days, beyond VaR — how bad the bad days really are), and the shape of the return distribution: skewness (negative = crash-prone, a long left tail) and excess kurtosis (high = fat-tailed, outlier-prone). The asset endpoint returns one instrument's full tail-risk profile; the screener endpoint ranks the cross-asset universe (equities, sectors, commodities, bonds, FX and crypto; filterable by class) from the most tail-risky to the safest. This is the cross-asset distribution-tail / VaR-CVaR cut — distinct from the bring-your-own-series risk-metrics engine, the crypto-only coin risk scorecard, the drawdown-pain (Ulcer) screener and the volatility APIs. It is the left tail, measured across the whole book. ## 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/tailrisk-api/..." ``` ## Pricing - **Free** (Free) — 640 calls/Mo, 2 req/s - **Starter** ($12/Mo) — 14,700 calls/Mo, 6 req/s - **Pro** ($37/Mo) — 81,000 calls/Mo, 16 req/s - **Mega** ($84/Mo) — 466,000 calls/Mo, 40 req/s ## Endpoints ### Screener #### `GET /v1/screener` — Rank the universe by tail-risk metric **Parameters:** - `metric` (query, optional, string) — cvar, var, kurtosis or skew Example: `cvar` - `confidence` (query, optional, string) — Confidence level: 95 or 99 Example: `95` - `window` (query, optional, string) — Lookback in trading days (60-1000) Example: `252` - `class` (query, optional, string) — equity, sector, commodity, bond, fx, crypto or all Example: `all` **Example:** ```bash curl -H "x-oanor-key: $KEY" \ "https://api.oanor.com/tailrisk-api/v1/screener?metric=cvar&confidence=95&window=252&class=all" ``` **Response:** ```json { "data": { "note": "Ranked by cvar over window_days of daily returns at 95% confidence. VaR = daily loss not exceeded on 95% of days; CVaR (expected shortfall) = average loss on the worst 5% of days. Negative skew = crash-prone; high excess kurtosis = fat-tailed. Losses are reported as positive percentages. Read fresh per call, nothing cached.", "class": "all", "count": 20, "metric": "cvar", "safest": { "symbol": "HYG", "cvar_pct": 0.62 }, "source": "Yahoo Finance", "results": [ { "name": "Silver", "rank": 1, "class": "commodity", "symbol": "SLV", "cvar_pct": 9.7, "skewness": -2.184, "available": true, "observations": 252, "var_hist_pct": 4.89, "confidence_pct": 95, "excess_kurtosis": 13.926, "var_parametric_pct": 5.88, "daily_volatility_pct": 3.77 }, { "name": "Ethereum", "rank": 2, "class": "crypto", "symbol": "ETH-USD", "cvar_pct": 8.53, "skewness": -0.002, "available": true, "observations": 252, "var_hist_pct": 5.49, "confidence_pct": 95, "excess_kurtosis": 2.564, …(truncated, see openapi.json for full schema) ``` ### Asset #### `GET /v1/asset` — Full tail-risk profile of one instrument **Parameters:** - `symbol` (query, required, string) — Universe symbol Example: `SPY` - `confidence` (query, optional, string) — Confidence level: 95 or 99 Example: `95` - `window` (query, optional, string) — Lookback in trading days (60-1000) Example: `252` **Example:** ```bash curl -H "x-oanor-key: $KEY" \ "https://api.oanor.com/tailrisk-api/v1/asset?symbol=SPY&confidence=95&window=252" ``` **Response:** ```json { "data": { "name": "S&P 500", "note": "VaR is the daily loss not exceeded on 95% of days (historical percentile and normal parametric); CVaR is the average loss on the worst 5% of days. skewness < 0 means a long left tail (crash-prone); excess kurtosis > 0 means fatter tails than a normal distribution. Read fresh per call, nothing cached.", "class": "equity", "reads": { "cvar": "contained tail risk", "skew": "crash-prone (long left tail)", "kurtosis": "fat-tailed" }, "source": "Yahoo Finance", "symbol": "SPY", "cvar_pct": 1.8, "skewness": -0.324, "window_days": 252, "observations": 252, "var_hist_pct": 1.35, "confidence_pct": 95, "excess_kurtosis": 1.526, "var_parametric_pct": 1.19, "daily_volatility_pct": 0.78 }, "meta": { "timestamp": "2026-06-12T10:34:47.026Z", "request_id": "8616273f-73e2-40c7-b055-1cfb6d146380" }, "status": "ok", "message": "Asset tail risk retrieved successfully", "success": true } ``` ### Universe #### `GET /v1/universe` — The cross-asset universe and its classes **Example:** ```bash curl -H "x-oanor-key: $KEY" \ "https://api.oanor.com/tailrisk-api/v1/universe" ``` **Response:** ```json { "data": { "note": "The cross-asset universe the screener ranks. Pass class= to a screener call to rank within one class.", "count": 20, "assets": [ { "name": "S&P 500", "class": "equity", "symbol": "SPY" }, { "name": "Nasdaq 100", "class": "equity", "symbol": "QQQ" }, { "name": "US Small Caps", "class": "equity", "symbol": "IWM" }, { "name": "Developed ex-US", "class": "equity", "symbol": "EFA" }, { "name": "Emerging Markets", "class": "equity", "symbol": "EEM" }, { "name": "Technology", "class": "sector", "symbol": "XLK" }, { "name": "Financials", "class": "sector", "symbol": "XLF" }, { "name": "Energy", "class": "sector", "symbol": "XLE" }, { "name": "Health Care", "class": "sector", "symbol": "XLV" }, { "name": "Utilities", "class": "sector", "symbo …(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/tailrisk-api/v1/meta" ``` **Response:** ```json { "data": { "note": "metric is cvar (default), var, kurtosis or skew. confidence is 95 (default) or 99. window is 60-1000 trading days (default 252). class filters to equity/sector/commodity/bond/fx/crypto (default all). Losses are reported as positive percentages. Read fresh per call, nothing cached.", "source": "Yahoo Finance daily closes, live", "classes": [ "equity", "sector", "commodity", "bond", "fx", "crypto" ], "metrics": [ "cvar", "var", "kurtosis", "skew" ], "service": "tailrisk-api", "endpoints": { "GET /v1/meta": "This document.", "GET /v1/asset": "Full tail-risk profile of one instrument (symbol=SPY, confidence=95, window=252).", "GET /v1/screener": "Rank the universe by tail-risk metric (metric=cvar, confidence=95, window=252, class=all).", "GET /v1/universe": "The cross-asset universe and its classes." }, "description": "Cross-asset tail risk — ranks the major markets by how brutal their bad days are, live from Yahoo Finance daily closes (no key, nothing stored). For each market it returns Value-at-Risk (historical and parametric, 95%/99%), Conditional VaR / Expected Shortfall (average loss on the worst days), and the return-distribution shape: skewness (crash-proneness) and excess kurtosis (fat tails). asset re …(truncated, see openapi.json for full schema) ``` --- Marketplace page: https://www.oanor.com/api/tailrisk-api OpenAPI spec: https://www.oanor.com/api/tailrisk-api/openapi.json