This is a strong project idea. The "100 small tools" format makes it easy to follow, and keeping each tool free/open-source gives people a reason to come back as the collection grows.
The current set already covers useful developer utilities: URL metadata, redirects, rate limiting, AI summaries, and file conversion. Those are exactly the kind of small tools people often need once and do not want to sign up for.
One thing that could make the project even more useful is adding a simple "request a tool" or voting section, so people can suggest which utility should be built next. That would also make the public build-in-public angle stronger.
Nice work so far. 9/100 is already a solid start.