api documentation
What it is
API documentation explains how another person or program can use an API. Good documentation describes the available operations, required authentication, request and response data, errors, limits, examples, and version expectations.
Think of a delivery service’s instruction card. It tells a partner where to deliver a package, which label is required, what proof of delivery looks like, and what to do when an address is invalid. The card does not deliver the package itself.
Why it exists
An API may work perfectly for its own team yet be unusable by partners if they must guess URLs, fields, permissions, and errors. Documentation turns an internal implementation into an interface other people can adopt and support.
Key ideas
- A human-readable guide should explain intent, prerequisites, authentication, common tasks, constraints, errors, and support or versioning expectations.
- An OpenAPI description is a machine-readable API contract. It can generate reference pages, client code, and tests, but it does not replace examples and decision guidance written for people.
- API documentation must match the deployed API. Treat contract changes as release changes and test them with representative clients.
- Azure API Management’s developer portal can publish managed APIs and products so consumers can discover them, learn how to use them, request access, and try them. Portal visibility or a “Try it” console does not remove authorization requirements.
- Write examples with safe sample values. Never publish real API keys, customer data, or production secrets in documentation.
Northwind example
Northwind documents its partner order-status API with a quickstart, an OpenAPI reference, expected errors, a sample request, and the scopes a delivery partner needs. The developer portal lets an approved partner find the API and request access. When Northwind adds an optional field, the docs and contract change together. Before removing an existing field, the team publishes a versioned migration path so partners do not discover the break after deployment.
Documentation versus the API gateway
| Component | Main job |
|---|---|
| API documentation | Help a consumer understand and use the contract correctly. |
| [[openapi | OpenAPI description]] |
| [[api-management | API Management]] |
Documentation supports access; it does not authenticate a caller, enforce authorization, or guarantee backend behavior.
Common confusion
- A developer portal can show an API that a visitor is not entitled to call. Discovery and access control are separate decisions.
- An interactive console can send real requests. Use suitable test data and protect operations that change production data.
- “Documented” does not mean stable forever. Consumers need versioning and deprecation communication.
Related
openapi · api-management · api-access · api-policies · deployment · northwind-traders-case-study
Sources and re-audit
- Microsoft Learn — Overview of the developer portal in Azure API Management, checked 2026-09-16.