I think online tools is not a bad idea, but a lot of the tools there are low quality and gimmicky, like anything that can be done in your head, or using a pocket calculator / trivial spreadsheet:

https://www.kodytools.com/commission-calculator https://www.kodytools.com/half-your-age-plus-seven-calculato... etc...

Perhaps it would be better to split out the financial tools (bonds, cagr, interest) from the programmer/text tools stuff.

I do actually think online / browser based tools that people hit via search for very occasional / niche uses is a good idea, e.g.:

https://everytimezone.com/ http://gc.kls2.com/

For these, they do non-trivial things, and are also a combination of a tool / logic plus some embedded reference data (timezones / DST, airport locations, etc) - I think that's the key. Maybe try fewer, higher quality tools with dedicated domain names instead of quantity.