I added support for alt text in my hack to autopost to Mastodon. MarsEdit doesn’t support saving alt texts into the corresponding WordPress field due to some API limitation, so I had to get them from the img tags directly. The whole effort involves several things I am not super familiar with. In addition to PHP and WordPress, I had to relearn XPath to query the markup for img alt attributes and then modify the raw form data to include them as descriptions. Not fun, but worth it.