# Evaluation Use Cases

## Supplying the External Entity ID

To supply an External Entity ID when [creating a new Evaluation](https://developer.alloy.com/public/reference/post_evaluations), you can use either a request header, or a field in the request payload.

* As a header, you can supply the External Entity ID using the `Alloy-External-Entity-ID` key:
  ```curl
  curl -X "POST" "https://sandbox.alloy.co/evaluations" \
       -u WORKFLOW_TOKEN:WORKFLOW_SECRET \
       -H "Content-Type: application/json" \
       -H "Alloy-External-Entity-ID: yourExternalEntityId" \
       -d $'{
         "name_first": "John",
         "name_last": "Doe"
  }'
  ```
* Alternatively, you can also put the External Entity ID directly in the payload under `identifiers.external_entity_id`:
  ```curl
  curl -X "POST" "https://sandbox.alloy.co/evaluations" \
       -u WORKFLOW_TOKEN:WORKFLOW_SECRET \
       -H "Content-Type: application/json" \
       -d $'{
         "name_first": "John",
         "name_last": "Doe",
         "identifiers": {
            "external_entity_id": "yourExternalEntityId"
         }
  }'
  ```

## Retrieving the Entity Token

In the Alloy evaluation response, you can retrieve the Entity Token from the `entity_token` field:

```json JSON
{
	"status_code": 201,
	"error": null,
	"timestamp": 1687555034666,
	"evaluation_token": "L-jhJl58RzXTr0c9AoRy7K",
	"entity_token": "P-pcxJQPzEJ4v54RmUS6RW",
  ...
}
```