An API Catalogue is a view of your business products expressed as technical services as visible to internal and external consumers to facilitate fast and self-service integration to deliver richer value to end customers and deliver it faster
An API Catalogue lets your customers view and interact with your product brouchre
A catalogue item can be in a design state or from implemented services, viewers of this catalogue are able to play with these services in either case

Catalogued services display ownership of the product and its performance via technical and business metrics leading to a shared understanding of impact to the business over time. Good API catalogues are also a great signal of API maturity to your partners leading to greater collaboration and rapid innovation in a partner eco-system with new value uncovered together!
There are many benefits from this approach, below are my top 5 reasons for why API catalogues are needed by business today
5 reasons how an API catalogue can help your business grow
#1 Catalogues can be aspirational and accelerate your business strategy
Instead of describing capabilities you have accumulated, re-imagining capabilities based on your business strategy as technology services (APIs) can help internal and external teams orient to your strategy better. Compared to a service registry the vision is delivered via left shift of design vs waiting for a service to be deployed

Catalogues accelerate integration with consumers, growing your presence in market and paying for themselves
API Catalogues make it easier for consumers to search, discover and play with your services. Catalogues provide sandboxes, allowing consumers to test integration and provide versioned interfaces in early design to allow consumers to change with the provider. The catalogue fosters an as-a-service communication model leading to autonomy across teams and increasing uptake by consumers. This further leads service teams to focus core business vs consumer integration support

Catalogues drive innovation and collaboration within internal teams and with partners in an eco-system of teams
A catalogue can host descriptions of services during early design and host executable samples of these in a sandbox; this allows consumers and provides to rapidly iterate on design versions independently

Sharp API Catalogues signal integration maturity to partners
A standardised, well documented catalogue with a good sandbox and examples goes a long way in signalling to potential business partner teams that integrating with you will be a breeze! There are digital strategists, product managers, developers on the other side who are keen to build new partnerships but see the pain of integrating with old-school techniques as a major hurdle. Do you offer easy self-service onboarding, discovery and integration to your APIs through the catalogue?
Catalogues foster unification and measurement of your digital services
API catalogues can host not only interfaces for APIs but also other services including events and message subscriptions leading to a unified view of services provided. Adding live service monitoring statistics along with key customer centric metrics such as Net Promoter Score (NPs) to a catalogue can not only add show how well a product is performing but also drive proactive marketing, refining etc
Summary

An API Catalogue is a view of your business product strategy expressed as technical services and visible to internal and external teams. A catalogue item can be in a design state or from implemented services, viewers of this catalogue are able to play with these services in either case
Catalogued services can show ownership and measurement from a technical and business perspective leading to a shared understanding of impact of services across business line.
Good API catalogues are also a great signal of API maturity to your partners leading to greater collaboration and rapid innovation in a partner eco-system with new value uncovered together
Getting started and rolling out a good catalogue can be challenging, I am curious to know what you have tried, lessons you might have learned and if you need support with unleashing this capability to your consumers and partners