You will want to do this before requesting a list on behalf of a user. This endpoint will return the user’s email address, the credits they have available, and whether or not they are subscribed.
In order to submit a task, the user must have enough credits, and they must be subscribed. Each contact you request costs credits_per_contact credits, so the largest task a user can afford is credits_available / credits_per_contact contacts. For example, 1000 credits at 5 credits per contact covers 200 contacts. A task that needs more credits than the user has available is rejected with a 400 status code and a descriptive message. If either of these are not true you should direct the user to Coldlytics to top-up their balance, or subscribe to a plan.
GET '<https://api.coldlytics.com/v2/user>'
{
"email": "[email protected]",
"credits_available": 1000,
"credits_per_contact": 5,
"is_subscribed": true
}