Service specification writing

Our company Keynetiks is a content hosting service who serve and host web sites and applications for end user customers. The goal of the project is to specify the Azure web hosting features to enable the capabilities of Azure app service plan to host static web sites, dynamic web applications and also the Azure PAAS app plan.
The specification document must describe the high level architecture, the features and components to use for affordable and secure service delivery. Identify use cases and stories to assess and implement in the context of agile Devops project management. subscription management, service management and component management.