API documentation with examples that are executed in CI

Goal

Documentation whose examples cannot drift from the API, because the same example files are validated, executed and rendered.

Prerequisites

An OpenAPI document that is the contract; a sandbox or test server with stable seed data; a CI pipeline in the API repository. The OpenAPI 3.1 specification (cited) defines Example Objects with either a value or an externalValue, expects each example to be compatible with its schema and says tooling may validate that compatibility automatically and reject incompatible examples. Python's doctest (cited) shows the underlying idea: text that looks like an interactive session is executed and checked to work exactly as shown; rustdoc (cited) likewise executes documentation examples as tests.

Steps

1. Write one example per operation and per documented error, as files referenced from the OpenAPI document through externalValue or as named examples entries; name each after its scenario (create-order-missing-address).
2. Validate every example against its request or response schema in CI; fail the build on mismatch.
3. Execute the request examples against the sandbox in CI. Compare the actual response with the documented response example, ignoring fields declared volatile (ids, timestamps) and failing on everything else.
4. Render the documentation from the same files: reference pages, the quickstart and SDK snippets include the example files instead of pasted copies.
5. For code samples in several languages, generate them from the examples with one template per language and run each against the sandbox; a sample that is not executed is a pasted copy and will drift.
6. When an example fails after an API change, decide explicitly: either the change is a bug, or the example and the prose change in the same commit as the API.
7. Print the CI verification date on the documentation page so readers can tell a maintained page from a stale one.

Expected result

Every example on the site has run against a live server since the last API change; readers and agents can copy a request and receive the documented response.

Limits and test basis

Examples exercise documented paths only and are not a test suite. Sandbox seed data must be stable or the comparison step becomes noise. The protocol is proposed; no reduction in documentation defects is claimed.