---
title: "Api V2 Signals Advanced Vol-Expansion Get"
method: GET
path: "/api/v2/signals/advanced/vol-expansion"
tags: ["Trade Signals (v2)"]
---

# Api V2 Signals Advanced Vol-Expansion Get

`GET /api/v2/signals/advanced/vol-expansion`

## 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/advanced/vol-expansion`
- Auth: HTTP bearer

Volatility expansion forecast — expansion readiness + directional bias.

Answers two questions at once: *Will vol expand?* (GEX-driven) and
*If it does, which way?* (momentum-driven).

**Logic highlights** (`src/signals/advanced/vol_expansion.py`):
- `expansion = gex_readiness × 100` (0–100); short-gamma regimes raise readiness.
- `direction_score = tanh(momentum_z / 1.0) × 100` based on a 5-bar z-score.
- `score = (expansion × direction_score) / 100` — sign matches direction,
  magnitude gated by expansion readiness.

**Params:** `symbol` (default `SPY`). Returns 404 when no data exists.

**Returns:**
```json
{
  "underlying": "SPY", "timestamp": "...",
  "clamped_score": 0.42, "weighted_score": 0.084, "weight": 0.20,
  "direction": "bullish",
  "score": 42.0,
  "expansion": 78.4,
  "direction_score": 53.5,
  "magnitude": 41.9,
  "expected_5min_move_bps": 14.2,
  "context_values": { "...full engine context..." },
  "score_history": [{"score": 42.0, "timestamp": "..."}, "...up to 90"]
}
```

- `score` — [-100, +100]; product of expansion × direction, scaled.
- `expansion` — [0, 100]; GEX-driven vol-expansion readiness.
- `direction_score` — [-100, +100]; momentum-driven directional bias.
- `magnitude` — [0, 100]; absolute size of the combined signal.
- `expected_5min_move_bps` — forecasted 5-minute move in basis points.
- `direction` — `"bullish"` | `"bearish"` | `"neutral"`.
- `score_history` — up to 90 recent `{score, timestamp}` points, newest→oldest.

**Trader interpretation:**
- `expansion > 60` + `|direction_score| > 50` → high-conviction expansion;
  long gamma or directional debit spread in the direction sign.
- `expansion < 30` → wait; dealers long gamma, likely pinning.
- Direction-score sign-flip while expansion stays high → whipsaw warning.

**Page design.** Two half-circle gauges (expansion + direction_score), a
"expected 5-min move" number (bps), and a sparkline of `score_history`.
Color the card green/red by direction when `|score| ≥ 25`.

## 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

---

[API](https://skmtc.dev/zerogex/apis/zerogex-api.md) · [All operations](https://skmtc.dev/zerogex/apis/zerogex-api/llms.txt) · [OpenAPI document](https://skmtc.dev/zerogex/apis/zerogex-api/revisions/753b26bf0592?raw)