billing-integration

What this skill does

# Credyt Integrate

> **Prefer the official SDKs** (`@credyt/api-client` for TypeScript, `credyt-api` for Python) over hand-rolling HTTP calls — they handle auth, retries, and field mapping for you. If neither SDK suits your stack (e.g. a language other than TypeScript or Python), HTTP direct calls are also covered below. If you arrived here without running `billing-setup` first, stop and ask the user to run that skill before proceeding.

Help the user wire Credyt into their application code. This skill works with the user's actual codebase — reading their existing code and adding Credyt integration in the right places.

The full integration guide is at [docs.credyt.ai/ai-integration.md](https://docs.credyt.ai/ai-integration.md). Each section below links to its dedicated docs page, which includes HTTP, TypeScript, and Python examples — consult these if you need more detail on any integration area.

> **Field naming:** The Credyt API uses `snake_case` for all fields. The TypeScript SDK maps these to `camelCase` automatically. The Python SDK keeps `snake_case`. Code samples in the linked docs show all three.

## Understand the codebase first

Before writing any code, understand what the user has:

> "Let me look at your project to understand your stack and where billing should plug in."

Check for:
- Language and framework (Node/Express, Next.js, Python/FastAPI, etc.)
- Authentication setup (how users sign up and log in)
- Where the billable activities happen in their code
- Existing environment variable patterns

## Choose the integration approach

Determine the right approach from context — only ask the user if you genuinely cannot tell.

**Auto-detect (in order):**

1. **Known AI platform** — Lovable, Bolt, Replit, and V0 all default to TypeScript. If running in one of these, use the TypeScript SDK.
2. **Existing tech stack** — check the codebase scanned above. `package.json` → TypeScript/Node.js SDK. `requirements.txt` or `pyproject.toml` → Python SDK.
3. **Unclear** → ask: *"Are you working in TypeScript/Node.js, Python, or another language?"* and lead with SDK options for the first two.

Once determined, state the recommendation and give the user the option to override before writing any code:

> "Based on your stack, I'll use the **TypeScript SDK** (`@credyt/api-client`). Let me know if you'd prefer Python or direct HTTP calls."

SDK packages:
- **TypeScript/Node.js** → `@credyt/api-client` (`npm install @credyt/api-client`)
- **Python** → `credyt-api` (`pip install credyt-api`)
- **Other language or preference for raw HTTP** → direct API calls with the `X-CREDYT-API-KEY` header

The full SDK reference with examples for all three approaches is at [docs.credyt.ai/sdk](https://docs.credyt.ai/sdk).

## Integration areas

Walk through each area. Not all will apply to every user — ask which ones they need.

### 1. API key setup

The Credyt API key must be stored securely on the server side — never in code that runs in the browser.

Add `CREDYT_API_KEY` to their environment variables alongside their other secrets, then initialise the client once and reuse it across requests.

**TypeScript:**
```typescript
import { CredytApiClient } from "@credyt/api-client";
const client = new CredytApiClient({ key: process.env.CREDYT_API_KEY! });
```

**Python:**
```python
from corehttp.credentials import ServiceKeyCredential
from credytapi import CredytApiClient

client = CredytApiClient(
    credential=ServiceKeyCredential(key=os.getenv("CREDYT_API_KEY")),
)
```

**Direct HTTP:** Attach `X-CREDYT-API-KEY: <key>` to every request. Create a helper function or configured HTTP client instance that sets this header automatically.

### 2. Customer creation — [docs](https://docs.credyt.ai/quickstart/create-a-customer)

When a new user signs up in their app, create a matching Credyt customer. Find their registration/signup handler and add customer creation after successful account creation.

Key points:
- Use `external_id` to link the Credyt customer to their app's user ID
- Subscribe the customer to the relevant products during creation
- Store the Credyt customer ID in their database alongside the user record
- Handle the case where the customer already exists (409/422 — look up by `external_id` instead)

**SDK method:** `client.customers.create(...)`

**Recurring fixed fees — pending subscriptions**

If the product uses a recurring fixed fee (e.g. $20/month), the customer must pay upfront before their subscription activates. In this case the API returns a `pending` status rather than activating immediately.

Set `return_url`, `failure_url`, and `redirect_to` on the subscription so Credyt knows where to send the customer after payment:

- `return_url` — where to send the customer after successful payment (e.g. `https://yourapp.com/account`)
- `failure_url` — where to send them if payment fails (e.g. `https://yourapp.com/callbacks/payment-failed`)
- `redirect_to` — set to `"return_url"` so the customer lands back on your site instead of staying in the Credyt billing portal (this is the default, but set it explicitly)

When the response status is `pending`:
- Check the `required_actions` array for an action with `type: "payment"` and extract its `redirect_url`
- Redirect the customer to that URL — Credyt will handle the payment form and route them to your `return_url` or `failure_url` automatically
- Do not activate the user's account yet — store it as pending in your database until payment is confirmed
- If the redirect link expires before the customer completes payment, fetch the customer by their Credyt ID to get a refreshed link

Once the customer pays, Credyt fires a `subscription.activated` webhook. Listen for this event on your backend and use it to activate the user's account.

**Promotional or bundled signup credits**

If the user's plan includes promotional credits (e.g. "start with $10 free") or bundled credits (e.g. 1,000 free API calls on signup), there are two ways to apply them:

1. **One-off adjustment after customer creation** — credit the customer's wallet directly post-signup. Use this for simple, one-time promotional amounts. See [docs.credyt.ai/advanced-topics/adjustments-charges-gifts](https://docs.credyt.ai/advanced-topics/adjustments-charges-gifts).
2. **Entitlements** — configure promotional credit as part of the product definition so it applies automatically on every new subscription. Use this for credits that are part of the standard plan offering. See [docs.credyt.ai/features/product-catalog/entitlements](https://docs.credyt.ai/features/product-catalog/entitlements).

Ask the user whether they want to include signup credits, and if so which approach fits their use case.

### 3. Usage event tracking — [docs](https://docs.credyt.ai/quickstart/send-usage)

Find where the billable activities happen in their code and add event submission after each one. Each event needs:

- A unique ID (UUID) so the same event can't be billed twice
- The correct `event_type` matching the product configuration
- A timestamp of when it happened (`occurred_at`)
- Any data fields needed for pricing (volume fields, dimensions)

**SDK method:** `client.events.sendUsage(...)` (TS) or `client.events.send_usage(...)` (Python).

For **volume-based** products, the event data must include the volume field (e.g., `total_tokens: 1500`).
For **dimensional** products, include the dimension values (e.g., `model: "gpt-4"`).

### 4. Cost tracking — [docs](https://docs.credyt.ai/features/profitability)

If the user set up vendors in `/credyt:billing-setup`, add cost data to usage events. Each event can include a `costs` array with the vendor ID, the amount it cost, and the currency.

This is typically added right after the billable action completes, when the cost is known (e.g., after receiving the response from an AI API that includes token counts).

> "Even if you're not charging users yet, attaching costs to every event lets Credyt calculate your unit economics so you can make pri