---
title: "Api V2 Signals Basic Skew-Delta Get"
method: GET
path: "/api/v2/signals/basic/skew-delta"
tags: ["Trade Signals (v2)"]
---

# Api V2 Signals Basic Skew-Delta Get

`GET /api/v2/signals/basic/skew-delta`

## Request

- Base URL: `https://api.zerogex.io` (the document declares no server; this is the origin it was published from)
- URL: `https://api.zerogex.io/api/v2/signals/basic/skew-delta`
- Auth: HTTP bearer

Short-dated OTM put-vs-call IV deviation — real-time fear gauge.

Answers: *are traders paying an unusual premium for downside protection
right now?* Equity-index skew is structurally positive (OTM puts always
trade richer than OTM calls), so this signal scores the **deviation
from normal**, not the raw spread. Bid-up put skew typically moves
*before* the tape confirms bearishness — useful leading-indicator.

**Logic highlights** (`src/signals/basic/skew_delta.py`):
- `spread = otm_put_iv − otm_call_iv` from `ctx.extra['skew']`
  (populated by the unified engine from `option_chains` near ATM).
- `deviation = spread − SIGNAL_SKEW_BASELINE` (default baseline 0.02).
- `score = −clip(deviation / SIGNAL_SKEW_SATURATION, [-1, 1])`
  (default saturation 0.04). Negative sign: elevated put skew → bearish.
- **Abstains (score=0)** if `otm_put_iv` or `otm_call_iv` is missing.

**Params:**
- `symbol` (default `SPY`). Returns 404 if no row exists yet.

**Returns:**
```json
{
  "underlying": "SPY", "timestamp": "...",
  "clamped_score": -0.35, "score": -35.0, "direction": "bearish",
  "weighted_score": 0.0, "weight": 0.0,
  "otm_put_iv": 0.192,
  "otm_call_iv": 0.147,
  "spread": 0.045,
  "deviation": 0.025,
  "context_values": {
    "otm_put_iv": 0.192, "otm_call_iv": 0.147,
    "spread": 0.045, "baseline": 0.02, "deviation": 0.025
  },
  "score_history": [{"score": -14.1, "timestamp": "..."}, "...up to 90"]
}
```

- `score` / `clamped_score` — `[-100, +100]` / `[-1, +1]`; negative = fear bid.
- `otm_put_iv` / `otm_call_iv` — IV as a fraction (e.g. `0.18` = 18%). `null` if missing.
- `spread` — `otm_put_iv − otm_call_iv`; typically `[0, 0.10]` for SPY. `null` if missing.
- `deviation` — `spread − baseline`; sign drives the score (positive → bearish score).
- `context_values` — the above plus `baseline` (the neutral-skew reference).
- `score_history` — up to 90 recent points.

**Trader interpretation.**
- `score < −40` → meaningful fear bid; tighten longs, consider downside hedges.
- `score > +30` (rare, call skew) → potential upside squeeze / short-covering setup.
- Steady negative drift while price rallies → distribution / bull-trap warning.
- `otm_put_iv == null` → no short-dated data this cycle; not the same as neutral.

**Page design.** Bidirectional ±100 gauge labeled "fear" (left) / "euphoria"
(right). Below, a two-line mini-chart of `otm_put_iv` and `otm_call_iv` as
% IV over `score_history` length, with a horizontal reference line at
`baseline` (the "normal skew" line). Color the gauge card red when
`score ≤ -40`, green when `score ≥ +30`.

## Query parameters

- `symbol` string

## Response `200`

Successful Response

- EnvelopeAny
  - `data` unknown, required
  - `freshness` Freshness, required: The v2 freshness envelope. Present on every ``/api/v2/*`` response.
    - `evaluated_at` string, date-time, required: When the API evaluated this response (server wall clock, UTC). Endpoint-health signal: advances on every request even when the underlying data is unchanged.
    - `generated_at` string, date-time, required: When the served data was computed. Equals the snapshot stamp for cycle-backed endpoints, or evaluated_at for endpoints computed on demand for this request.
    - `source_timestamp` string, date-time, nullable: Timestamp of the upstream market observation the payload derives from. This is what freshness_status is measured against. Null when the endpoint has no upstream feed or returned no rows.
    - `latest_event_at` string, date-time, nullable: Newest event timestamp present in the payload (last bar, last trade, last scored row). Best-effort on very large responses, which are sampled rather than fully walked.
    - `age_seconds` number, nullable: evaluated_at - source_timestamp, in seconds. Null when source_timestamp is null.
    - `market_session_status` string, required: pre-market | regular | after-hours | closed (US/Eastern).
    - `expected_update_cadence` string, nullable: ISO-8601 duration for how often this endpoint's data is expected to change right now, e.g. PT60S. Null means no updates are expected (weekend, holiday, or a feed that only runs during the session).
    - `expected_update_cadence_seconds` number, nullable: expected_update_cadence as a number of seconds.
    - `cadence_profile` string, required: Identifier of the cadence class this endpoint belongs to, e.g. analytics_cycle. Stable across releases; the seconds behind it may be retuned.
    - `stale_after` string, date-time, nullable: Instant after which this payload should be treated as stale. Null whenever expected_update_cadence is null.
    - `freshness_status` 'fresh' | 'aging' | 'stale' | 'session_closed' | 'static' | 'unknown', required: The rolled-up freshness verdict for one response. ``fresh`` ``source_timestamp`` is within one expected update cadence. ``aging`` Past one cadence but not yet past ``stale_after`` — the grace band that absorbs normal cycle jitter. Not an error; a client that polls faster than the cadence sees this routinely. ``stale`` Past ``stale_after`` while updates *were* expected. This is the actionable state: the feed behind this endpoint is late. ``session_closed`` A feed-backed endpoint whose feed is not due to produce anything right now (weekend, holiday, or a feed that only runs during the session). The payload is the last good value — deliberately NOT reported as ``stale``, because an overnight consumer polling a closed market is not observing a fault and should not page on it. ``static`` The endpoint is not feed-backed at all: completed history, or a result computed from the caller's own inputs. Age here carries no health meaning and never becomes a fault. ``unknown`` No source timestamp could be resolved from the payload (e.g. a pure calculator, an admin endpoint, or an empty result set). A consumer should fall back to ``evaluated_at`` for endpoint health and make no claim about data age.

## Other responses

- `422`: Validation Error

---

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