Our is public. To maintain our service level we ratelimit the number of API calls. For public API calls this is 60 API calls a day with distribution of 5 calls an hour. For paid plans this limit is increased according to the service level described in the plan.
For public calls you don't need to pass any API key. Just invoke the endpoint (see examples below). For paid subscriptions you need to pass the API key.
Currently we support API Key based authentication. Please set a request header 'X-Textart-Api-Secret' with value of your API key. Alternatively you can also pass api_key= as a request parameter, though we strongly discourage this mode of passing the key.