A lot of small SaaS APIs have decent docs.

Some even have an OpenAPI spec.

But no real sandbox.

That sounds fine until a developer tries to integrate the API and needs to test the part that docs cannot prove:

Does the workflow actually hold together?

Not one request.

The workflow.

The problem is not the first 200

Most API docs can show this:

POST /customers → 201 Created

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That is useful, but it is not enough.

For a real SaaS integration, the next questions are usually:

Can I read the same customer back? Does the subscription attach to the right customer? Does the webhook fire? Does my app know which user should get access?…