How to use Webwrite to call REST APIs successfully, eg OpenAI API

2 min readApr 3, 2023

Webwrite Produces Error Though Seemingly Identical CURL Request Is Successful at Calling OpenAI API

This matlab code doesn’t work. Can anyone figure out why?

prompt = 'Hello, how are you today?';
data = struct('prompt', prompt, 'temperature', 0.7, 'max_tokens', 60);
options = weboptions('RequestMethod','POST','MediaType','application/json','KeyName','Authorization','KeyValue','Bearer xxx');
response = webwrite(url,data,options)

The code generates a server error:

The server returned the status 400 with message “Bad Request” in response to the request to URL

https://api.openai.com/v1/completions.

This code was based on a working CURL example below that successfully calls the openAI API.

In each case, the Authorization xxx is replaced with a functional openAI api key.

Working CURL:

## cURL
curl -X "POST" "https://api.openai.com/v1/chat/completions" \
     -H 'Content-Type: application/json' \
     -H 'Authorization: Bearer xxxxx' \
     -d $'{
  "model": "gpt-3.5-turbo",
  "messages": [
    {
      "content": "Hello!",
      "role": "user"
    }
  ]
}'

This is running on a Mac with up to date OS. This is true using Matlab 2022b or 2023a prerelease.

NOTE:-

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I created the following function. This is both a working example of how to call rest apis, and a working example of how to call the openAI Chat api. It remains unclear to me why we need to use matlab.net and why webwrite doesn’t work, given that this would apepar to be webrite’s function.

function [result,tokens] = openAIChat(content)
%openAIChat Call openAI REST API for chat completions
%   Detailed explanation goes here
tic
import matlab.net.*
import matlab.net.http.*

% Define the API endpoint Davinci
api_endpoint = "https://api.openai.com/v1/chat/completions";% Define the API key from https://beta.openai.com/account/api-keys
api_key = "xxxxxxx";data = jsondecode('{"model":"gpt-3.5-turbo","messages":[{"role":"system","content":"You are a helpful assistant."},{"role":"user","content":"What is my birthday?"}]}');
data.messages(2).content = content;

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