Quick and Dirty ChatGPT Proofreader

While I find ChatGPT's reliability dubious when it comes to difficult real-life questions, I found one niche where it functions almost flawlessly - proofreading.

For many non-native speakers (or me at least), pinning down all details of English language (especially getting those pesky indefinite articles at correct places) might be difficult. ChatGPT, at least to my untrained eye, seems to do a really nice job when it comes to correcting the output.

And yes, one can use its chat interface directly to do the proofreading, but ChatGPT's API is reasonably cheap so you might as well make use of it.

var apiEndpoint = "https://api.openai.com/v1/chat/completions";
var apiKey = "sk-XXX";

var httpClient = new HttpClient();
    = new System.Net.Http.Headers.AuthenticationHeaderValue("Bearer", apiKey);

var inputText = File.ReadAllText("<inputfile>");
inputText = "Proofread text below. Output it as markdown.\n\n"
    + inputText.Replace("\r", "");

var requestBody = new {
    model = "gpt-3.5-turbo",
    messages = new[] {
        new {
            role = "user",
            content = inputText,

var jsonRequestBody = JsonSerializer.Serialize(requestBody);
var httpContent = new StringContent(jsonRequestBody,
                                    Encoding.UTF8, "application/json");

var httpResponse = await httpClient.PostAsync(apiEndpoint, httpContent);
var responseJson = await httpResponse.Content.ReadAsStringAsync();
dynamic responseObject = JsonSerializer.Deserialize<dynamic>(responseJson);

string outputText = responseObject.GetProperty("choices")[0]


And yes, this code doesn't really check for errors and requires a lot more "plumbing" to be a proper application but it does actually work.

Happy proofreading!

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