Grammar Checker API Documentation

The Virtual Writing Tutor provides a web service for checking the spelling, grammar and punctuation of any text in English. Our grammar checker API allows for the integration of proofreading services into any website or application. This page documents the API.

This webpage is intended for programmers only. English language learners should go to the grammar checker page to login for a free member's account.

Need help with installation? Contact us for an affordable installation service.

We require users to register for an API key*. To generate an API key*, fill in the form below and click the "Generate" button.

*Note: If you already have a essay checker API key, then there is no need to generate another. We recommend that you use same API key.


vwtApiKey : xxxxxxxxxx*

*(This is the generated API key)
POST { "text" : "He has go to beach by his friend Jane." } { "status": "1", "message": "Successfully checked", "error_grammar_count_total": 3, "error_grammar_percent": "34%", "check_grammar_feedback": [ { "context": "He has go to beach by his friend Jane.", "error_grammar": "has go", "feedback_grammar": "You probably need a past participle here. Try this instead: \"gone\". (pp99)", "feedback_grammar_suggestion": [ "gone" ] }, { "context": "He has go to beach by his friend Jane.", "error_grammar": "beach", "feedback_grammar": "You need a definite article here. Revise: \"the beach\". (ap25)", "feedback_grammar_suggestion": [ "the beach" ] }, { "context": "He has go to beach by his friend Jane.", "error_grammar": "by", "feedback_grammar": "Use \"with\" instead. Try this: \"with his friend Jane\". ", "feedback_grammar_suggestion": [ "with his friend Jane" ] } ] }

If an error occurs, you'll get a response like this:

{ "status": "401", "message": "unauthorized, You may need an valid api key to get access or may renew your subscription plan." }

The usual cause is a bad API key or the grammar checker is updating and so unavailable for 30 seconds while the system loads the new rules.

Screenshots (Postman)

This call checks one word at a time. The VWT grammar checking service is provided at

Make sure to add 'Content-Type:application/x-www-form-urlencoded' in headers.


For any call you have to use POST.


textThe word to check.Required. This is the data to check.
appKeyYour API key.Required. This is your API key (You need to generate it first if you haven't yet).


A typical response will look like this:

key : text
value : frgg

response : { "mistake_spelling": "frgg", "suggestion_spelling": "frig, frog, forgo, freq" }

Screenshots (Postman)


*(xxxxxxxx) is your API key
N/AGET { "jsonrpc": "2.0", "status": true, "result": [ { "client_name": "xxx", "client_email": "xxx", "api_key": "xxxxxxxx", "used_essay_hits": 1, "total_essay_hits": 100, "remaining_essay_hits": 99, "used_grammar_hits": 100, "total_grammar_hits": 100, "remaining_grammar_hits": 0 } ] }

If you send a text of 1 to 100 words for grammar checking, your account will be debited 1 call because the system registered 1 hit. You can check one thousand 100 word texts with the $5 USD 1000-call package, which is equal to half of a cent per 100-word text. If you buy a million calls at a time for $500, you will be able to check one thousand 100-word texts for a fiftieth of a cent each.

Spell checking is more expensive as each word is a separate call and will therefore register a separate hit.

See below for the price list

No.Package NamePriceDuration(in months)Total hitsAction

Want free calls?

Link to the VirtualWritingTutor on a webpage or blog with the keyword "grammar check" and contact us with your API username and a link to the page with the published link. We also offer free calls when you promote the VirtualWritingTutor on social media. Just contact us with the link(s).


  • The API user will publicly display a hyperlink to on the website where the API is used, crediting the Virtual Writing Tutor.
  • Bokomaru Publications, the owner and operator of, will endeavor to maintain uninterrupted service for the duration of the paid subscription to the API, but the API user acknowledges that Bokomaru Publications will not be held liable for interruptions of service.

I agree to these terms and conditions: