API Discovery with Developer Portals, Catalogs and Marketplaces: Finding the Right Tool for API Consumers

API Discovery refers to the ability to identify, catalog, and document all APIs used within an organisation with the goal of making them discoverable and usable while strengthening governance. There are countless tools that support API discovery. Typically, they are called developer portal, catalog, or marketplace. With this abundance of different names, it's easy to lose track. What should an API discovery tool actually accomplish? And which name is right for which type of tool?

Developer Portal

Developer portals provide access to APIs as self-service, seamless onboarding, good documentation, and integration support. Their main target audience is technical, which is also represented by the name.

The typical functions supported by a developer portal are:

• API documentation
• Interactive API exploration and sandboxes
• SDKs, sample code, Bruno / Postman Collections
• Authentication & API key/token management
• Support for development teams

A good developer portal helps development teams understand how to use an API. It reduces the time needed for integration, even during first use. Additionally, it increases the adoption rate for APIs through the self-service offering.

Catalog

Catalogs organise and manage APIs for better discoverability and consistency. Their main target audience is usually technical and internal to the company, as they provide a complete overview that is often not necessary for external users.

The typical functions supported by a catalog are:

• Centralised API inventory
• Search, filtering & categorisation
• Visualisation of API metadata
• Governance and policy enforcement
• Standardisation of API contracts and dependencies

A good catalog leads to APIs being reused because they are easier to find. This also reduces duplicates and API sprawl. It promotes governance through the enforcement of policies and consistency across team boundaries. Through the centralised API inventory, a catalog also enables standardisation of API contracts and dependencies.

Marketplace

Marketplaces connect API providers with their consumers and promote monetisation and partnerships. Their target audience is more diverse and includes people with both business and technical focus. Marketplaces are usually offered externally and show only a selected subset of the API landscape.

The typical functions supported by a marketplace are:

• Ratings, reviews, and community engagement
• Billing mechanisms and revenue sharing
• Legal agreements and transparent SLAs
• Onboarding of providers and consumers
• Pricing models for APIs

A good marketplace extends API usage beyond internal teams. It primarily supports the commercialisation and monetisation of APIs. At the same time, it must enable decision-makers to effectively monitor their API usage.

Consumer Needs

Discovery tools are the window to an organisation's API landscape. The most important stakeholders are the consumers of the APIs, who typically have four needs:

• Discoverability: Which API is right for my use case?
• Onboarding: How can I get started immediately?
• Integration: Is the API stable, reliable, and secure?
• Business alignment: What does using the API cost me?

The presented types of discovery tools focus on different needs:

Consumer Need	Developer Portal	Catalog	Marketplace
Discoverability	❌ Not the primary focus	✅ API metadata, categorisation, taxonomy	✅ APIs listed based on pricing or ecosystem fit
Onboarding	✅ Tutorials, interactive documentation, SDKs, sandboxes	❌ Not a core function	❌ Limited to API descriptions
Integration	✅ Self-Service	❌ Primarily a governance tool	❌ Pre-built integrations, API contracts
Business Alignment	❌ Mostly developer-centric	✅ Supports API lifecycle governance	✅ Enables monetisation and partnerships

A Tool for API Owners

In addition to developer portals, catalogs, and marketplaces, API registries are also emerging. Registries manage API artefacts to create transparency throughout their lifecycle. Their main target audience is API owners.

The typical functions supported by a registry are:

• Versioning & change tracking
• Central storage of API definitions
• Schema and dependency detection
• Lifecycle management

A good registry ensures transparency of the API lifecycle. It improves collaboration between teams and provides structured access to all API artefacts. In contrast, Portals, catalogs, and marketplaces focus on the consumption of APIs. The registry is thus the central and authoritative data source for all discovery tools used internally and externally.

The API registry serves as the central storage for API artefacts. From here, APIs are synchronised to various access channels such as developer portals, catalogs, and marketplaces, where they are made available to different target groups of consumers.

Conclusion

Different API discovery tools also have different focuses. Depending on whether the audience is purely technical or should include business stakeholders, a different tool should be used. The different tool types also have various tasks. While registries and catalogs tend to regulate the lifecycle of the API and provide an overview of all APIs, developer portals and marketplaces focus on the consumption of APIs.

Overview of the typical target audience (horizontal axis) and the typical task (vertical axis) of different tool types for API discovery.