Material Design's writing guidelines (part of Google's Material Design system) cover UX text principles: short scannable text, simple direct language, and consistent point-of-view (second person "you/your"), extending into data visualization and onboarding copy patterns.
Free: part of the open Material Design system documentation.
Designers and writers working within Android/Google-ecosystem products wanting writing guidance consistent with Material Design's broader visual and interaction system.
Note the URL structure has evolved. Material Design has progressed through versions (M2, M3), so confirm you're referencing the current guidance (m3.material.io) rather than an archived older version.
Google's writing guidelines within the Material Design system.