For what it's worth, Sapling.ai (a Y Combinator startup) offers an SDK with grammar/spell checking as well as other LLM-powered functionality. Disclaimer: I'm on the team.
Author of one of the detectors here (Sapling.ai). We try and be clear that the detector output should be used as just one of many possible cues and that there will always be false positives. That said, detectors often do detect bland/generic text, and that can be useful feedback. Open to other suggestions: [email protected]
Don't mind the subscription pricing -- keeps all parties aligned.
The UI toolkit is especially exciting, been looking for something to replace streamlit.