payment intent

The three are defined by the protocol that names them. A charge intent defines one-time payments, for a client paying once for a resource. A session intent defines metered pay-as-you-go payments, for usage that is frequent. A subscription intent defines recurring fixed payments, for access that renews. A pay-per-call endpoint is asking for a charge.

Naming it in the challenge is what makes the difference readable from outside. The payment challenge MPP defines carries intent as a required parameter beside the payment method, the challenge identifier and the protection realm — so the commitment and the price arrive in the same response. The Internet-Draft behind the protocol takes it further and defines the intent as a registered value, with each intent specified in a document of its own.