The unique identifier for an API is usually just a slugified version of the name of the API, if the name conforms to some standard. The purpose of the API identifier, or simply aid, is to provide a unique human and machine-readable identifier that will be unique across API operations, or even possibly an industry.
The aid for an API will be prepended with the aid for the API contract the API is located in, and should reflect the resources and capabilities being made available. Depending on the strategy for an API provider, the aid might be able to be autogenerated from the name of the API, or might need some additional manual touches to ensure uniqueness.
Having a unique identifier for each API is an often overlooked aspect of producing API products, standardizing their identification as we would any other product. Having aid for each individual API resource and capability, combined with aid for each domain, line of business, or team, becomes how you inventory APIs across the enterprise API factory floor.