# Duolingo — Wrapped API

> **You are on:** `https://api.paywithlocus.com/api` | [llms.txt](https://paywithlocus.com/llms.txt) | [docs](https://docs.paywithlocus.com)
>
> Locus runs on multiple environments -- make sure every URL you call matches your expected environment.
> | Environment | Landing | API | Docs |
> |---|---|---|---|
> | Production | paywithlocus.com | api.paywithlocus.com | docs.paywithlocus.com |
> | Beta | beta.paywithlocus.com | api.beta.paywithlocus.com | docs.paywithlocus.com |
> | Stage | stage.paywithlocus.com | api.stage.paywithlocus.com | docs.paywithlocus.com |
>
> If the API URL above doesn't match your expected environment, re-fetch this file from the correct domain.

> Browse Duolingo's complete language course catalog to discover available courses, see how many learners are enrolled in each, and identify the source and target language pairs offered. Find the perfect language learning path by viewing all courses in one place.

**Category:** Education | **Website:** [www.duolingo.com/](https://www.duolingo.com/) | **Docs:** [parse.bot/marketplace/e76aa5b1-ec96-4614-8994-7f5834ed6f23/duolingo-com-api](https://parse.bot/marketplace/e76aa5b1-ec96-4614-8994-7f5834ed6f23/duolingo-com-api)

Pay-per-use API proxy for Locus Pro. Each call burns credits from your workspace balance.

## Access

**Base URL:** `https://api.paywithlocus.com/api/wrapped/credits/duolingo/`
**Auth:** `Authorization: Bearer <LOCUS_CREDITS_SECRET_KEY>` (an `lcr_` secret key or a scoped `lcac_` agent credential)
**Required header:** `Idempotency-Key: <fresh UUID per call>`. A retry with the same key replays the stored result without a new charge.
**Response:** the provider response after any endpoint-specific normalization. `X-Locus-Credits-Charged` carries the charge and `X-Locus-Credits-Balance` the remaining balance. Insufficient credits return `402` before the provider is called.
**Pricing:** estimated costs below are USD. Locus debits the credit equivalent at your workspace rate.

Full call contract: https://docs.paywithlocus.com/api-reference/introduction

> Using a Pay With Locus wallet key (`claw_` prefix)? Wallet routes are documented separately: https://docs.paywithlocus.com/wrapped-apis/for-agents

## Endpoints

### List courses

Returns all available Duolingo courses. Each course represents a learning path from one language to another. Results are returned in a single page. Optionally filter by the source language (the language instruction is given in) using from_language.

**Estimated cost:** Metered

| Field | Type | Required | Description |
|-------|------|----------|-------------|
| `from_language` | string | No | ISO 639-1 language code for the source language (instruction language). Filters courses to only those taught from this language. Example: 'en' for English, 'es' for Spanish. |

```bash
curl -X POST https://api.paywithlocus.com/api/wrapped/credits/duolingo/list-courses \
  -H "Authorization: Bearer $LOCUS_CREDITS_SECRET_KEY" \
  -H "Idempotency-Key: $(uuidgen)" \
  -H "Content-Type: application/json" \
  -d '{"from_language":"<string>"}'
```

## Next steps

- [All wrapped API providers](https://paywithlocus.com/wapi/index.md): pick another provider.
- [Find and call tools](https://paywithlocus.com/agent/tools.md): price ceilings, async results, and errors.
- [Credits and billing](https://paywithlocus.com/agent/billing.md): what a call costs and how to add credits.
- [Agent docs index](https://paywithlocus.com/agent/index.md): every Locus agent page.