# Corp Actions Reconciler > Reconcile a position file against splits, dividends, and spinoffs to catch breaks before they hit P&L or T+1 settlement. Use when an operator hands over a CSV of positions and asks "are these right after the recent corporate actions." Runs on a free Massive Basic key. - Skill: `rgourley/corp-actions-reconciler` (Agent Skill, multi-file: 9 files) - Install (CLI): `npx skillmds@latest add rgourley/corp-actions-reconciler` - Raw SKILL.md: https://api.skillmd.com/api/skills/rgourley/corp-actions-reconciler/raw - Safety review: pending - Works with: Claude Code, Claude.ai, OpenAI Codex - Category: Data & Analytics - Author: rgourley (https://skillmd.com/u/rgourley) - Updated: 2026-09-17 - Page: https://skillmd.com/skills/rgourley/corp-actions-reconciler --- # corp-actions-reconciler You hand over a CSV of positions. The skill walks every line against the splits and dividends history, flags anything where the recorded share count or cost basis is off, and emits a clean reconciliation report with citations. This is the highest-grounding-value workflow in the suite. LLMs hallucinate split factors constantly (was it a 3-for-1 or 7-for-1? forward or reverse?). Massive's splits endpoint has the truth, so the skill never guesses. ## When to invoke - Operator says "reconcile my positions" or "check this CSV against corporate actions" - A monthly close turned up a position-file break and you want to find which corporate action caused it - Before a T+1 settlement window when a stale position file would break settlement instructions ## What you need - A position file in CSV format with columns: `ticker`, `shares`, `cost_basis`, `as_of_date` - A Massive API key (free Basic tier works) - `MASSIVE_API_KEY` exported in the environment ## What you get back The skill ships two output layers: **Layer 1: canonical JSON** matching [`output-schema.json`](./output-schema.json). This is what UI dashboards, downstream agents, and Python scripts consume. Every field is typed, every break carries its source endpoint and a fetched-at timestamp for audit trail. **Layer 2: rendered exception report** for Claude Code users. See [`references/rendering.md`](./references/rendering.md) for the full rendering rules. A short example: ``` 2 BREAKS found across 47 positions checked. BREAK 1: AAPL Recorded: 100 shares as of 2024-08-01 Action: 2-for-1 split, ex-date 2026-03-10 Expected: 200 shares Delta: +100 (under-allocated) Source: api.massive.com/v3/reference/splits?ticker=AAPL Verified: 2026-06-23T14:32:08Z ``` UI devs work from the JSON. Claude Code users see the rendered form. Same compute, two consumption surfaces. ## How it works 1. For each row in the input CSV, call the splits and dividends endpoints with `ticker` and `execution_date > as_of_date` (splits) and `ex_dividend_date > as_of_date` (dividends). 2. Apply each split's `split_to / split_from` ratio to the recorded share count, in chronological order. Cost basis moves inversely. 3. Walk dividend records and route by Massive's `dividend_type`. RC (regular cash) and SC (special cash) reduce cost basis per share by the cash amount. SD (stock dividend) and LT (large stock dividend, treated as a split per IRS Rev. Rul.) adjust share count and prorate basis. ST routes through the split path defensively. Unknown types are surfaced in `tier_caveats` rather than silently dropped. See [dividends methodology](./references/dividends-methodology.md). 4. Read spinoff entries from a `spinoffs.json` overrides file (no dedicated Massive spinoffs endpoint as of June 2026); adjust the parent position's basis and create a new position for the subsidiary at the issuer's allocation. See [spinoffs methodology](./references/spinoffs-methodology.md). 5. Compare projected share count and cost basis to the recorded values in the input file. 6. Emit any mismatch as a BREAK with citation. The four methodology references are the IP. Read them in this order if you're extending the skill: 1. [`splits-methodology.md`](./references/splits-methodology.md): forward and reverse splits, compounding, fractional results. 2. [`dividends-methodology.md`](./references/dividends-methodology.md): cash, special, RoC, stock dividends, timing rule. 3. [`spinoffs-methodology.md`](./references/spinoffs-methodology.md): parent basis allocation, new-position creation, Massive endpoint gaps and override file format. 4. [`edge-cases.md`](./references/edge-cases.md): CIL, ADR/ordinary mapping, reverse-split delisting watch, symbol changes, same-day actions, FX. ## Endpoints used - `GET /v3/reference/splits` (paginated; one call per ticker) - `GET /v3/reference/dividends` (paginated; one call per ticker) - `GET /v2/aggs/ticker/{ticker}/range/1/day/{spin_date}/{spin_date}` (only when computing first-session cost-basis allocation for a spinoff) The splits and dividends endpoints are included in the free Basic tier. Rate-limited to 5 calls/min on free, so a CSV with more than ~50 rows will take a few minutes on a free key. Any paid tier eliminates the wait. The aggs call for spinoff basis allocation also runs on Basic. ## Example ```bash # Quick test against a small position file echo "ticker,shares,cost_basis,as_of_date AAPL,100,150.00,2024-08-01 GOOGL,50,2800.00,2022-06-01" > positions.csv # Invoke from Claude Code # > /corp-actions-reconciler positions.csv ``` The skill processes positions sequentially and writes a single JSON + rendered report at the end of the run. ## Foundations used - [`massive-api-patterns`](../massive-api-patterns) for auth and rate limiting ## Doesn't handle (yet) - Tender offers and exchange offers - Mergers (cash, stock, and mixed consideration) - Rights offerings (subscription rights) - Currency-redenominated cost basis (FX conversion of basis is the operator's settlement-system problem; see edge-cases.md) - ADR ratio changes that the splits endpoint misses (workaround: manual entry in `spinoffs.json`) Add these in a PR if you need them. The patterns are straightforward extensions of the existing splits/dividends/spinoffs logic.