Access openai with HTTPRequest but body parameters seems not function

Question

Using Mathematica 13.0 on Windows 10

codes are below

req=HTTPRequest["https://api.openai.com/v1/completions",
<|Method->"POST",
"Body"->{"model"->"text-davinci-003","prompt"->"Say this is a test"},
"Headers"->{"Authorization"->"Bearer sk-xxxxxxxxxxxxx"}|>]
URLExecute[req]

and here is the output

{error->{message->you must provide a model parameter,type->invalid_request_error,param->Null,code->Null}}

It seems I set the wrong body parameters especially in "model" part.

First I checked the openai Ducuments to set proper body parameters.Then I used postman to verify my body parameters and it works. However, when I try to reproduce POST request in Mathematica, the output returned by the site shows that I did not set body parameters correctly.

I also checked my request body by using

req["Body"]

and it returns normally

{"model": "text-davinci-003","prompt": "Say this is a test"}

I think the possible error is in setting the wrong format or position of the parameter. Could anyone give me some suggestions or hints on setting body parameter?

Answer 1

According to Kuba's and GustavoDelfino's comments, the solution is to make sure to send a JSON body with a proper content-type header:

req = HTTPRequest[
  "https://api.openai.com/v1/completions",
  <| 
    Method -> "POST", 
    "Body" ->   ExportString[{"model" -> "text-davinci-003",      "prompt" -> "Say this is a test"}, "JSON"], 
    "ContentType" -> "application/json",
    "Headers" -> { "Authorization"-> ...} 
  |>
]

URLExecute[req]