Your text exceeds the limit of 1500 characters (it's 3979 characters).

I’m trying to write a plugin for Neovim to check grammar, but I’m getting the error in the subject line. The API docs say that I should be able to submit up to 20,000 characters on the free account.

" * maximum number of characters per request: 20,000 (free) / 60,000 (Premium)"

Is there a free API key or something to make this work? I looked, but I couldn’t find anything.

For non-premium users, please use as the endpoint.

That did it. I must have overlooked that. Thank you for your help!