Looks kewl, my take is that kind thing is the hardest thing to market because it's not just one thing it's a whole lot of things.
From an SEO perspective I think you want a landing page for each and every one of the tools so that somebody who is searching for a particular tool might find it. For that matter you also want a landing page for each category of tool so you should have one for "music tools".
Effective promotion is a lot more work than you might thing but involves following every angle you can, for instance you want to promote the music tools for people who are into music.
Another hint is that you should have some metadata so that if somebody shares it on social it automatically loads a good image because people only click on things on social if they have a good image (I think). Mastodon didn't find an image for it so I took a screenshot and added it here:
https://mastodon.social/@UP8/115016800036776060
When I go to a page like
https://kewltools.com/emoji-search-copy
it starts out scrolled way down to a panel of the other tools and I have to scroll up to find the tool which is undesirable because I'd really like to bookmark that one so I can always find it. When I trigger a scroll inside that tool it winds up scrolling the whole page and then I see the other tools and have to scroll back up. I think it would be better to see just that tool on that page.