Specify both file content and body content in openapi

In my web application, when I create a form-data object that looks like the following:

let fd = new FormData();
let data = {};
data.id = 5; // thing id, if this is an existing thing
data.thingName = 'Resource Test'; // actual value from modal form
data.thingType = 'Type Check'; // actual value from modal form
data.relatedThingId = 19; // actual value from modal form, if bar selected
fd.append('thing', JSON.stringify(data));
fd.append('file', values.file?.file);
const upload = await axios.put('/things', fd);

the 'thing' key along with it's corresponding stringified 'data' is loaded into request.body by axios, while the file object corresponding to the 'file' key is loaded into request.Files.file. I've found I can model the file portion of the request in my openapi document by doing the following (although I don't know if this is the correct way to do it:

put:
  description: creates or updates a thing record
  requestBody:
    required: true
    content:
      multipart/form-data:
        schema:
          properties:
            file:
              type: object
              properties:
                name:
                  description: the name of the file being stored
                  type: number
                mimetype:
                  description: the mimetype of the file
                  type: string
                data:
                  description: the body of the file
                  type: string
                  format: binary