# Services CallBack

To receive a response after using the init issuance and init verification APIs, it is necessary to define an endpoint and specify it in the callback parameter within both services.

### Verification CallBack

When using the verification API, it is possible to receive the results of the verification process automatically via a callback.
The `callback_url` parameter specifies the URL where the verification results will be sent, providing access to the Wallet user’s presented claims.

To enable this, you must create a callback endpoint and provide its URL in the API request using the `callback_url` field. Once the verification process is completed, the results will be sent to this endpoint.

Key points of the callback:

- Must be a POST endpoint, meaning that the URL receiving the callback must accept HTTP POST request.
- Receives a JSON body containing verification results.
- Even if the request includes **multiple credentials** (`verification_template_ids`), only one callback is sent with all results, avoiding multiple requests.


**Example JSON Callback**


```json
{
   "state" : "123456789012",
   "code": "abc123",
   "tokens": {
       "1": {
           "token": "eyJhbGciOiJIfUzI1NiIsInR5cCI6IkpXVCJ9...",
           "status": "COMPLETED"
       },
       "2": {
           "token": "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9...",
           "status": "FAILED"
      }
   }
}
```

**Fields Description**

- **state**: value passed when calling the API; defaults to none if not provided.
- **code**: unique code returned during verification initialization; used for additional security check.
- **tokens**: dictionary where keys are verification_template_ids of credentials and values contain:
  - **status**: human-readable verification status; if not "COMPLETED", the verification is considered failed (KO).
  - **token**: JWT (JSON Web Token) of the verification (to be decoded), including:
    - **iss**: base URL of the service that issued the JWT.
    - **jwks_uri**: endpoint to fetch the issuer’s public keys.
    - **vp_token**: token sent by the app (e.g., mdoc/sdjwt).
    - **verification_id**: unique ID of the verification.
    - **presented claims**: the actual verified data.


### Issuance Callback

It is possible to set a callback also for the issuance service.

The issuance callback is sent for each requested credential. If the issuance request includes multiple credentials (each associated with a different `template_id`), a separate callback will be generated for each credential.


```json
{
  "state": "1234567890",
  "code": "abc123",
  "template_id": 1,
  "status": "Issued",
  "completed": true

}
```

Parameters descrpition:

- **state**: the state value passed during initialization (init); if not specified, defaults to none.
- **Code**: the security code returned during initialization; used for an additional security check (double security check).
- **template_id**: the identifier of the processed credential template.
- **status**: the status of the credential. If the value is different from "Issued", the issuance is considered failed (KO).
- **completed**: a boolean indicating whether the interaction process between the Gateway and the wallet has finished (true) or is still in progress (false).