I was recently talking to a Thunderbird developer about API design. In the course of that conversation, I expressed concerns about RNP, the new OpenPGP implementation that Thunderbird has recently started using in place of GnuPG. That person, skeptical about my assertion that RNP’s API needs improvement, asked “Isn’t it subjective what a better API is?” I’d agree that we don’t yet have good metrics to evaluate an API. But, I disagree that we can’t judge APIs at all. In fact, I s...