How do you measure developer marketing effectiveness?

I like to think the developers create the long-tail of use cases for end users. With that, I measure in three dimensions: first, momentum in the platform; second, quantifying end user value; third, measuring impact to the business. In a B2B setting, a customer who has gone through the work of building a customized workflow on top of the developer platform is likely going to be harder for a competitor to take away because the switching costs are so much higher. So I look to measure developer marketing effectiveness (first) by the volume of actions that take place on the developer platform then (second) by the growth in consumer use cases by way of the platform with an ultimate goal (third) of creating additional business health (high ASP, low churn, etc.) In a B2C setting, the first two dimensions would be the same but the third dimension would be something around customer engagement–DAU for the integrations, engagement within a time frame for the cohort of users leveraging the integration vs those not, etc. 

Technical evangelists should be tracked by views and viewer retention rates that eventually lead you to the funnel metrics that marketers track. Ultimately you will want develoepr marketing to roll in to the regular metrics you track as a marketing leader with traffic, evaluations, active usage, customers, and revenue. 

Here's a short list which comes to my mind, some of them are obvious but I would think of this backwards i.e. what is the definition of success for every marketing strategy/tactic which you run:

• Website Traffic & Page Views, time on Site

• Downloads/Installs

• Community Participation online on social/forums etc- growth, engagement and churn of community, Likes, Views, Upvotes, Ratings, Comments/Answers etc

• API/SDK Integration - depth of integration

• Conversion Rates and CTRs

• Developer Surveys & Feedback

• Retention & Churn Rates