The Read tool loads a file into Claude's context. You can request a specific line range with offset and limit, which matters when a file has + lines and you only need the first .
The Write tool creates or replaces a file entirely. If the file exists, the whole thing gets overwritten. Claude uses Write when you say "create a new file" or when the destination doesn't exist yet. When you ask Claude to change something in an existing file, it reaches for Edit instead of Write, so you're protected from accidental full replacements. I'll cover Edit in detail next.