Solution:declare body value in your interface with next:
@Body RequestBody bodyand wrap String JSON object:
@Body RequestBody body
RequestBody body = RequestBody.create(MediaType.parse("application/json"), obj.toString());
there is chance of you kept same @SerializedName("") for multiple vairable/fields/tags
You can specify a Converter when you create the Retrofit like this
Retrofit retrofit = new Retrofit.Builder() .addConverterFactory(GsonConverterFactory.create()) .baseUrl(baseurl) .client(okHttpClient) .build();