Provide executable examples that users can type directly into their terminals to see working API calls. To the greatest extent possible, these examples should be usable verbatim, to minimize the amount of work a user needs to do to try the API.
If you use postman to test/mock API requests you can let it generate various kinds of examples, e.g.
curl -X POST -H "Content-Type: application/json" -d '{
"email":"john.doe@example.com",
"password":"test"
}' "http://service.com/api/session"