How to upload a file over JSON-RPC, when JSON has no type for a file

JSON has no representation for a file. Strings, numbers, arrays, objects - that is the whole list. So every JSON-RPC API eventually runs into the same question: how do you accept a file upload - a photo, a scan, a PDF - when the protocol itself cannot carry binary data? The usual answer is: you don't. The file goes to a separate, ordinary controller that reads $request->files , and the JSON-RPC layer handles everything else next to it. And now you have exactly the ad hoc endpoint sprawl that JSON-RPC was supposed to remove. In otezvikentiy/json-rpc-api 5.2 there is a different answer. And more interesting than the feature is how it came about: I did not write it - an external contributor did. But first things first. Full disclosure: I am the author of the bundle, and I have maintained it alone for almost three years. That is exactly why a release whose headline feature was written by someone else feels like a different kind of event to me. The problem Straight from issue #8 : two services exchange scanned images plus structured metadata (tenant, station, session) on the same call - something like captures.create(tenantId, stationId, image) . Today image cannot be expressed as a parameter of a JSON-RPC method, so that call has to live outside the bundle as a separate multipart controller. What you want is for the method to simply declare a parameter of type UploadedFile and get the file, like any other parameter. The solution: multipart as a transport adapter The key idea is to leave the core untouched. A multipart/form-data request is normalized into the very same JSON-RPC envelope an ordinary request produces, only with UploadedFile objects already sitting inside params . Everything below the transport - hydration, batching, validation - stays completely unaware of multipart, exactly the way it is unaware that a GET request's payload came from a query string. The wire format: one text part named jsonrpc carries the full JSON-RPC envelope as a string (all scalar par