MockFlow - My Favourite Wireframe Tool
When I got my first "real" job as a web designer/developer in 2000, I did a lot of learning on the job. I waded into the role with HTML and image editing skills, but that was about it. I needed to figure out Macromedia Coldfusion, MS SQL databases, and how to spin up ecommerce websites.
So I moved slow and broke things. I'd stay late in the office, wait till everyone left, then hack away at whatever website was in-flight, breaking and fixing it to figure out how it worked. It wasn't all bad - most of them worked out in the end - but the UX often left a lot to be desired.
From working closely with teams at Wix, Shopify, Microsoft, Trello (and many others) to build integrations with their Platforms, I've learned a ton about the value of visually articulating a vision upfront - before code is anything close to written.
For API development, visually exploring the potential ways it might be used is also useful.
Over time MockFlow has become my favourite tool for exactly that. The workflow is simple, the defaults are smart, and the export options are fantastic (including HTML, which can be quickly uploaded to a service like Netlify). Mockflow's free tier is pretty generous - give it a try.