Certain Wikibase API modules, e.g. SetClaim or SetReference, do have a field that must contain a JSON blob. Even if these API modules are not made to be used manually by a user, we want users to play around with the API and learn how it works. That's one of the reasons why we have the ApiSandbox.
Problem: It's not at all obvious how these JSON blobs should look like. Even if you try to copy and paste that JSON from a previous GetClaims request or an other source, you need to know which part of the JSON blob must be copied. What I currently do is looking at the actual PHP source of the API module plus a fair amount of trial and error.
Suggestion: Include a minimal example in the description. At least show the "header" of an example JSON blob so users can identify the required part(s) in a full entity blob. Warning: The example should not parse to avoid accidental copy-pastes. This can be achieved by replacing the "flesh" of the example with ….
(Related, but independent task: T98458.)