Dear Toolsie,
My next-door neighbor keeps 'borrowing' tools from my garage without asking and returning them late or damaged, and I don't know how to say something without it becoming A Whole Thing.
Toolsie's Take
You're not being petty. Tools are yours, and "borrowing" without asking is taking, no matter how friendly the neighbor is. The fact that they come back late or damaged makes it worse, because it means your things are being used without your say-so and then not even respected. That's a real boundary issue, not a minor annoyance you should just absorb.
Here's the thing: the longer you say nothing, the more you're teaching them that this is fine. You don't need a confrontation — you need a clear, calm statement. Something like, "Hey, I'm happy to lend things occasionally, but I need you to ask first, and I need them back on time and in the same condition. If something breaks, let me know right away so we can figure it out." That's not making it A Whole Thing; that's just stating the terms. If they react badly to a reasonable request, that tells you something about them, not about you.
What still needs your input is whether you even want to keep lending at all. You could just as easily say, "I'm not comfortable lending tools anymore," and that's completely valid — you don't owe anyone access to your stuff. But if you do want to preserve some neighborliness, the ask-first-and-return-in-good-shape rule is the minimum. Either way, the conversation is the same: set the boundary, and let their response guide what you do next. You're not responsible for managing their feelings about your perfectly reasonable request.