The body is in a format the endpoint does not accept — usually a Content-Type mismatch.
Frequently caused by the client, not the server: a forgotten Content-Type header, or a form encoding where JSON was expected.
1 endpoint in this playground answers with 415. Every one is free, needs no signup, and can be called from the browser or with curl.
POST https://funapi.dev/api/movies/v1/movies/{id}/poster — contentType is not an accepted image type (Movies API)All HTTP status codes · All 37 mock REST APIs · Getting started guide