Correct and natural are different questions
저는 친구와 주말에 카페에 갔습니다 is grammatically correct. In an ordinary conversation, 저 주말에 친구랑 카페 다녀왔어요 may fit more comfortably because it uses spoken vocabulary, drops information that is already clear, and chooses an everyday polite ending.
The formal version is not wrong. It can suit a presentation, report, interview, or a moment where the speaker intentionally wants distance. The useful question is not “Which sentence is always better?” but “Which sentence fits this relationship and situation?”
Five before-and-after examples
These examples show common changes supported by the tool. Read the note before reusing the result in a different situation.
Everyday polite; the subject is already clear.
Everyday question; 무엇을 contracts to 뭘.
A natural everyday request.
Polite without an announcement-like tone.
A conversational promise to follow up.
When you should not change the sentence
Keep -습니다/-습니까 when you are giving a formal presentation, reading an announcement, reporting to an audience, or deliberately using a professional register. Do not remove particles mechanically: Korean often omits them when the meaning is obvious, but contrast or emphasis can make the particle important.
Natural Korean also varies with age, relationship, workplace culture, and the speaker’s intention. If the tool cannot identify a supported pattern, treat the unchanged sentence as a prompt to ask for context rather than proof that every nuance is perfect.
Practice beyond copying
After checking a sentence, name the relationship first: friend, coworker, customer, teacher, or audience. Say the suggested version aloud, then rebuild it with one detail from your own life. Finally, return to the formal version and explain when you would choose it instead.
For example, change 저 지금 집에 가요 to 저 지금 회사에 가요 and 저 지금 카페에 가요. Then compare each one with the formal -갑니다 version. This turns one conversion into a reusable speaking pattern.