/sector-rotation-signal

name: sector-rotation-signal
description: Change-detection layer on top of market-regime. market-regime reports current sector leadership as a snapshot; this skill tracks how the leadership order has changed over a rotation window (default 30 days) and flags sectors moving up or down the ranks. Categorizes moves into growth / value-cyclical / defensive / rate-sensitive buckets and generates a plain-English theme read. Use when the daily regime hasn't moved but the composition of leadership is shifting — the actual tradeable signal.

sector-rotation-signal

You hand over a rotation window (default 30 days) and get back the current 20-day RS rank per sector, the rank change over the window, and a rotation classification (rotating in, stable, rotating out). Bundled with a plain-English theme read.

Rank change is the leading signal. The tape already prices absolute strength; leadership rotation is what tells you the composition of strength is shifting.

When to invoke

• The user asks "what sectors are rotating", "is the market rotating",

"growth vs value right now"

• market-regime shows the same label two days in a row but you want

to know if the underlying composition is changing

• Portfolio-review workflow, after market-regime — regime says WHAT,

rotation-signal says WHERE-IT'S-MOVING

• A single-name research question wants sector context: "is my

Tech position bucking the sector rotation"

What you need

• `MASSIVE_API_KEY` (Stocks Starter). One daily-aggs call per SPDR

sector ETF + SPY (12 calls total).

What you get back

**Layer 1 JSON** matching [`output-schema.json`](./output-schema.json). Per-sector: current 20-day RS rank, rank in the reference date, rank_delta, 20-day RS in basis points, secondary RS window, rotation classification, category tags.

**Layer 2 rendered table** sorted by current rank. Rotation column uses arrows (`↑`, `↑↑`, `↓`, `↓↓`, `stable`) so the visual read is immediate. Theme line above the table. See [`references/rendering.md`](./references/rendering.md).

How it works

1. **Fetch SPY + 11 sector ETFs** over `lookback_days` (default 252) using the same helpers as market-regime. 2. **Compute RS ranks on two reference days**: `now` (latest trading day) and `then` (latest trading day <= today - rotation_window). RS is `sector_return - spy_return` over the primary RS window (default 20 days), reported in basis points. 3. **Compute rank_delta** = rank_then - rank_now (positive means the sector moved UP the leadership order, i.e. rank number went DOWN). 4. **Classify each sector**: rotating_in_strong (delta >= +3), rotating_in (>= +2), stable (|delta| <= 1), rotating_out (<= -2), rotating_out_strong (<= -3). 5. **Generate theme read** based on which category buckets (growth, defensive, value-cyclical, rate-sensitive) are receiving inflows vs outflows.

Category tags

• **growth**: XLK, XLY, XLC
• **defensive**: XLP, XLU, XLV
• **value_cyclical**: XLE, XLI, XLB, XLF
• **rate_sensitive**: XLRE, XLU, XLF (overlap intentional)

Endpoints used

• `GET /v2/aggs/ticker/{ticker}/range/1/day/{from}/{to}` for SPY +

11 sector ETFs

Doesn't handle (yet)

• **A 1-position rank move is inside the noise floor.** Deliberately

classified as `stable`. Users who want fine-grain rotation should use a longer rotation window.

• **SPDR sector ETFs are a proxy for the full sector universe.**

Real-world sector performance can diverge from the ETF (especially in Energy, where XLE is oil-major heavy).

• **RS is past-return, not predictive.** Rotation captures a shift

in what's working, not what will work next.

• **Rotation reads are heuristic.** Real regime classification

belongs in a dedicated macro tool; this is a change-detection surface, not a regime call.