I'd say another rule of thumb, which may not be specific to developer marketing, is to avoid the "used by" pitfall. I often see tools that were launched, like, a month ago claiming that it's "loved by teams at Uber/Slack/etc". What I imagine in those scenarios is that there's an intern who signed up for a beta using their company email, and the founders were like "hey good enough, technically we're now used by teams at [x] company!" I can see through it, and I'm sure others can as well.

It comes off as disingenuous. A better way is to tell a specific success story. If some unknown brand has a story to tell about how your tool 10x'd their productivity, I'm all ears.