In my experience, a good target to aim for is a pair of manifestos containing 5-10 tenets each, with each one encapsulating a belief or value which is not wildly controversial but which also wouldn’t be universally held by all engineers in your organization by default.
I recommend formatting each Engineering Value or Architectural Principle as a catchy phrase, along with a sentence or two to describe the concept in more detail. Here’s a good example from Scout24’s Engineering Values:
Outcome over effort
We celebrate the impact of our work over the effort we’ve been putting in or the amount of code we produced. We understand the potential impact of our work to our business and search for an easy, fast, secure way to validate our ideas before writing any code.
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