We use - Service Specification (a service description is part of a specification) to describe the functional behavior 'contract' between the provider and all consumers. e.g. if the consumer provides a valid customer number, the provider will return the customer's name and address.
and - Service Level Agreement, to describe usage 'contract' between specific provider and consumer (though the same contract may be made between the provider and all consumers) e.g. if the consumer makes no more than 1000 requests per hour, the provider will respond in no more than 5 seconds. See http://cbdi.wikispaces.com/Service+Specification
