# `GET /ownership/transaction-types`

**Purpose:** The SEC transaction-code catalog — 20 codes with their official name and grouping.

**Response:** `transaction_types` (array of `{code, name, group}`), `source_url` (the SEC form the wording is copied from), and `credits_used`.

**Credits:** **0.** No charge, no usage entry.

**Errors:** `422 VALIDATION_ERROR` when any query parameter is sent.