> For the complete documentation index, see [llms.txt](https://docs.alternativepayments.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.alternativepayments.io/getting-started/3rd-party-tools/rewst.md).
# Rewst
Many MSPs use **Rewst** to automate workflows across PSA tools, billing systems, and third-party platforms. To enable automated invoice payments and customer operations via **Alternative Payments**, youโll need to authenticate and interact with our API directly through Rewst using HTTP Request blocks.
This guide walks you through how to **authenticate with the Alternative Payments API** inside Rewst, so you can securely trigger additional API calls from your workflows.
***
## :notebook\_with\_decorative\_cover:How It Works
Rewst supports HTTP requests through its workflow automation engine, allowing you to interact directly with external APIs like Alternative Payments.
To integrate with our API:
* **Authenticate using OAuth 2.0:** This authentication method is used to obtain secure, server-to-server access without user interaction.
* **Obtain an access token:** Upon successful authentication, the API returns an `access_token` that is valid for a limited time.
* **Authorize future requests:** Use this token in the `Authorization` header (`Bearer` format) to securely access other endpoints.
* **Follow standard REST practices:** All API interactions are based on REST conventions, using JSON payloads, HTTP methods, and header-based authentication.
***
## :sparkles:Step-by-Step### :closed\_lock\_with\_key: Step 1: Authenticate using HTTP Request Block
1. In your **Rewst workflow**, click **+** to add a new **HTTP Request** block.
2. Set **Request method** to `POST`.
3. Set **URL** to:
\
In the **Body** section, use:
```
grant_type=client_credentials
```
Set the following **Headers**:
Header
Value
Content-Type
application/x-www-form-urlencoded
Authorization
Basic your_base64_credentials
#### :key: Base64 Credentials
To generate the **base64** credentials:
* Format your credentials as `clientId:clientSecret`
You can find your clientId and clientSecret in the Partner Dashboard under the /pages/6sbv7bokaxdRfklInL3v section.
* Go to [https://www.base64encode.org](https://www.base64encode.org/).
* Paste the string and click **Encode**.\\
**Example**
Copy the result:
and paste it in the Authorization header as:
```
Basic base64_encoded_value
```
***
### ๐งช Step 3: Test the Request
1. Click **Test** in the HTTP Request block.
2. Then click **View Result**.
โ If successful, you will receive a JSON response containing:
Copy the `access_token`.
***
### ๐ Step 4: Use the Token in Future Requests
For any additional API calls (e.g., Listing customers, fetching invoices), include Authorization as a header:
```
Authorization: Bearer access_token
```
#### **๐ Example endpoint:**
**Request**
```
GET https://public-api.demo.alternativepayments.io/customers
```
**Response**
***
## :map:Flow
---
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