API Catalog SEO

API Catalog SEO is the practice of making an intentionally public API easy for developers, search engines, and compatible agents to find and understand. The useful asset is not a page that merely says “we have an API”; it is a maintained documentation surface connected to a correct interface description and real access rules.

OpenAPI provides a standard, language-agnostic way for humans and computers to understand HTTP API capabilities. It does not automatically publish, secure, index, or distribute the API.

Minimum Useful Publication Set

Asset	What it must answer
Overview page	Who the API is for and which user outcome it supports
OpenAPI description	Servers, paths, operations, parameters, schemas, and security schemes
Authentication guide	How credentials are obtained, scoped, rotated, and revoked
Quickstart	One complete request and response using a safe test path
Error reference	Status codes, error objects, retry behavior, and support path
Limits and pricing	Rate limits, quotas, cost boundaries, and fair-use rules
Version policy	Current version, compatibility rules, deprecation window, and changelog
Terms and data policy	Allowed use, retention, privacy, and restricted data

If a client cannot complete one safe request from the published material, the catalog is not ready.

Discovery Without Inventing Standards

Use stable, conventional links first:

• Link developer documentation from relevant product pages and site navigation.
• Give the API overview and specification stable canonical URLs.
• Include public documentation in the XML sitemap when it is intended for indexing.
• Link the downloadable OpenAPI description from the human-readable docs.
• Use registered HTTP link relations only when their semantics match.
• Use a /.well-known/ URI only when an applicable specification defines or registers it.

Do not create an arbitrary well-known path and claim that agents universally discover it. RFC 8615 defines how well-known URIs are registered; it does not make every invented path interoperable.

Content Quality Requirements

High-quality API documentation needs more than generated endpoint tables:

1. Explain the user job and the boundary of each operation.
2. Provide realistic examples with clearly fictional data.
3. Document authentication and authorization separately.
4. Show failure cases, idempotency, pagination, and retry behavior where relevant.
5. Keep examples synchronized with the deployed version.
6. Explain data freshness and fields whose meaning is easy to misread.
7. Publish migration notes before breaking changes.

Generated reference pages can be useful, but they should not be the only explanation of workflow, policy, and failure behavior.

API Catalog Versus Other Agent Surfaces

• Use OpenAPI for an HTTP service contract.
• Use an MCP server when compatible clients need live tools or resources through MCP.
• Use an Agent Skill to package reusable instructions around a task.
• Use an A2A Agent Card when a deployed A2A server accepts agent-to-agent tasks.

Do not mirror the same capability into every format unless each integration is real, owned, and tested.

Validation Checklist

• Every documented operation exists in the intended environment.
• Server URLs, authentication schemes, scopes, and examples are current.
• No internal hostnames, secrets, or private schemas are exposed.
• The OpenAPI document validates against its declared version.
• A new developer can complete the quickstart without undocumented steps.
• Error and rate-limit behavior match live responses.
• Canonical, sitemap, and internal links point to the preferred documentation URL.
• Ownership, changelog, and deprecation dates are visible.

For the longer implementation guide, see API Catalog SEO: How AI Agents Discover Your Public APIs. Related topics include Link Headers for AI Agents, Agent Skills Index, and Auth.md and OAuth Metadata.

Primary Sources

• OpenAPI Specification
• RFC 8615: Well-Known Uniform Resource Identifiers
• IANA Link Relation Types