Hello,
LanguageTool is an open-source grammar, style and spell checker. I’ve been using it for several months and love it.
I want to make a tentative feature request of integrating LanguageTool’s free public API into DEVONthink, so that users can take advantage of its tool set when writing inside DT.
Thanks in advance for evaluating my request! 
Have you tried using the Mac app they offer?
Yes, and it certainly does a great job of checking grammar, as advertised. But personally I prefer using LanguageTool in the form of integration with other apps rather than its standalone Mac app, because the integrations simply blend in seamlessly into the existing workflow while using the app is an extra layer of friction (i.e. it’s not a great text editor).
Apart from the official LanguageTool apps and add-ons on their website, there are also Ulysses (link, paid API), Obsidian (link, free API) and VS Code (link, free API) integrations that I use. It’s easier to open and edit plaintext and Markdown files from DT in VS Code (⌘⇧O), and I figured maybe it could make sense, business- and development-wise, for DT to integrate with LanguageTool so that it’s even easier.
The request is noted but no promises, of course.
Of course. Thanks, Jim! 
I just wanted to make the same suggestion. Ullyssess uses Language Tool and its foundation is open source. The Mac app does not open .md files unfortunately.
There is government funding behind this project and with the open source foundation and API, it may be something more attractive than Grammarly:
The request is noted. However, implementation isn’t simple just because there’s an API, open-source or not. This adds to development as well as support when there’s a problem.
PS: Notice this…
Yeah, the free public API is rate limited. If/when DT implements such a feature, perhaps it would be a useful design to limit the check rate on the client side to avoid exceeding the API rate limit.
At least, it would be great if one could open md files in their editor. I wrote to them whether this could be done. I would not mind paying for it - so maybe there is then at least some sort of integration for license owners.
Having had a look at their API (specially the JSON results), I’d say that this would require quite some work to implement in a useful way. Wow, now the browser plugin told me to do something about “in a useful way”.
If someone is running a Synology NAS, they could run the LanguageTool server on it and try it out. That has the charm that your text does not go anywhere else and that there’s probably no rate limitation. But you’d still have to build some tool(s) to analyze the JSON results.
Also, you’d need to figure out how the tool treats Markdown and other markup languages. There’s a provision to mark markup in the input to the API, but that looks incredibly cumbersome.
Maybe for the time being, using it in VSCode or some other writing tool where the stuff is already integrated with your own server would be a sensible workaround.
They currently do not support markdown, they told me (but will consider it, they say).
I used Ullysses for a while and found the language help useful. I then purchased a license for Antidote but the extra step, calling up the language check, did not work for me.
What Grammarly is doing looks great, checking while you type. With them, however everything one types goes through their servers … I am not an expert but it sounds a bit too much of checking.
Interestating is that they now go beyond spelling and grammar and make also suggestions on style.
Writeful is another interesting contender. They use an AI to learn their rules texts and have a nice integration with Overleaf. While some years ago we used translators to have fun, tools like DeepL have become really good. Natural language processing is making good progress.
For non-native speakers the development of such language tools is interesting.
ProWritingAid may also be of interest: https://prowritingaid.com
They can handle md files.
They argue that security and privacy is at the core of their product, e.g. being GDPR compliant
They integrate with Scrivener and have an API. Maybe they can be convinced to establish an integration with DevonThink as well?
A Desktop version of LanguageTool is being launched, might be of interest to see how it could cover Devonthink. Writing Assistant for Apple Mail and Notes (macOS)
I use it and really like it, especially since it manages to handle several languages at once. But: You’ll send everything to the LT server. Might not be advisable in some case (or even illegal in others). They assure us that they don’t store the data on their servers, but they have to read them, nonetheless.
One can run an LT server on (for example) a Synology (in a docker container), so the data remains at home, read more about that here: LanguageTool embedded HTTP Server | dev.languagetool.org. But then, you’d have to write all the integration stuff yourself 
They also offer an API, but that sets you back 39 € per month – probably a bit steep for most users.
And there’s the “LT Editor” that runs on macOS: You can copy/paste your text in it, it’ll check it, you can fix it in this editor and then copy/paste it back into your app. The same warnings apply, as also in this case the text is sent to their servers.
