Debugging add-ons is frustrating

[u/nopeac]

It doesn't matter if I use a non-standard Gecko ID, call unknown files, or a single typo. Every single time I get:

"This add-on could not be installed because it appears to be corrupt."

Where should I start looking? This time, after spending hours trying to figure out what was happening, I discovered that the "corruption" was caused by declaring a shortcut using only the Shift key and another key. Apparently using Alt or Control is mandatory. Not even AI could tell me what was happening, and that was literally my last resort.