Subject: Quick link on [Your Micro-Niche]

Hi [Name],

Hope you're having a great week.

My name is [Your Name], and I've been following your work on [Project or Area]. I was just reading through a discussion on Hacker News and found this new open-source tool for [solving a problem relevant to them/related to the space they work in].

[Link to the tool/comment/paper]

Thought of you and figured it might be interesting.

That's all, have a good one!

Best, [Your Name]