> ## Documentation Index
> Fetch the complete documentation index at: https://docs.userintuition.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# Reference catalogs and usage

> Read supported study settings and bounded interview usage from the public API.

The versioned public API provides read-only configuration catalogs. Each accepts the same API key or dashboard session as the other public endpoints:

| Endpoint | Returns |
| - | - |
| `GET /api/public/v1/reference/languages` | Accepted language codes, names, and native names, including `auto` |
| `GET /api/public/v1/reference/modes` | Supported interview formats |
| `GET /api/public/v1/reference/voices` | Public `male` and `female` voice values with display names |
| `GET /api/public/v1/reference/study-types` | Visible planning templates, paged and without internal prompts |
| `GET /api/public/v1/reference/study-types/{slug}` | One visible planning template |
| `GET /api/public/v1/usage/interviews` | Eligible interview counts, credits used, and resolved query scope |

Use the `voice` value when creating a study; the display name is informational. A study-type planning template describes a use case. Public study creation accepts `in-depth-interview`, `concept-test`, or `prototype-test` as the research method. Study-type responses omit internal planning prompts.

Usage accepts optional `start_date`, `end_date`, `cadence` (`daily`, `weekly`, or `monthly`), and `app_id`. Omitted dates resolve to an inclusive 30-day UTC range ending today. The response includes that resolved range and app in `scope`, so a zero total has a defined meaning. `total_interviews` counts eligible non-test interviews; `total_units` also includes non-refunded synthetic runs. Rows include bounded per-period counts and units.