Shopify's Polaris content guidelines cover voice and tone, accessible/inclusive language, grammar, naming conventions and error messaging: widely cited as a leading example of situational tone (e.g. light and casual for new-merchant onboarding vs. direct for error messages).
Free: part of the public Polaris design system.
Content designers wanting a well-regarded, publicly documented example of how tone should shift by context (onboarding vs. errors) within one consistent brand voice.
The situational-tone guidance (different tone for onboarding vs. errors, all within one coherent voice) is the standout lesson here, a good model to study before building a team's own context-sensitive tone rules.
Shopify's own content guidelines for consistent product writing.
