A discoverable catalog of APIs, packages, or related resources published by a provider — a single document that lists what exists and where to find it. The index is the entry point for both humans browsing an offering and machines crawling an ecosystem; it is what makes an API portfolio (rather than a single API) navigable.

Also known as: API Index, APIIndex, Catalog, API Catalog, PackageIndex, Package Index

Example

- type: Index
  url: https://developers.example.com/apis.json

Standards

• IETF RFC 9727 — api-catalog Well-Known URI
• Community APIs.json
• IETF Linkset (RFC 9264)
• Schema.org schema.org DataCatalog
• Schema.org schema.org ItemList

Well-Known Paths

• /.well-known/api-catalog — RFC 9727 — Discoverable catalog of an organization's APIs and supporting resources.

Media Types

• application/linkset+json — RFC 9264 — Default response shape for /.well-known/api-catalog.
• application/json — Used by APIs.json and ad-hoc catalogs.
• application/yaml — Common alternate serialization for APIs.json.

Link Relations

• index — IANA Link Relations
• collection — RFC 6573
• service-desc — RFC 8631

Risk & Compliance

Security: An index is an attacker's first stop — it enumerates surface area for free. Publish only intentionally public entries; never include staging, internal, or partner-only APIs in a public catalog. Treat the index as a publication boundary and validate it in CI.

Tools

• APIs.io — Public API search built on APIs.json catalogs
• Backstage Software Catalog — Internal catalog (Apache-2.0)
• api-catalog-cli — RFC 9727 tooling

Suggested Metrics

• catalog_freshness_days — Days since the index was last regenerated against the live API inventory.
• catalog_drift — Count of deployed APIs missing from the index, or indexed APIs no longer deployed.
• catalog_crawl_hits — Requests against /.well-known/api-catalog from known directories or aggregators.

Example Implementations

• U.S. General Services Administration — Federated catalog spanning multiple federal agencies.
• APIs.io — Public APIs.json-based catalog of API providers.
• AWS — Service-level index pointing into per-service documentation.

Related Properties

• Documentation
• Portal
• Openapi

Tags

• Discovery
• Catalog
• Inventory

All Common Properties