Build the toolkit around everyday use
Build the brand toolkit around the materials people need to create and maintain, not just the assets needed to launch an identity. For Sony TEOS, The Frameworks applied a professional visual identity across PowerPoint templates, product brochures and splash screens. The shared style drew partly on isometric representations of working environments, connecting different formats through a recognisable visual approach.
The Frameworks also describes a designer whose company introduced a new identity without supplying the assets needed to apply it to an existing app. The company had concentrated on materials for marketing without involving designers, leaving a central customer experience unsupported.
The practical starting point is to ask the people applying the brand which formats they use and what they need to update. Include customer-facing applications alongside marketing documents where relevant. A toolkit should make the identity usable in everyday production, rather than leave creators to bridge the gap between guidelines and working materials.
Sources: Sony TEOS: Brand Identity, The inside story: why your people shouldn't be just passengers on your brand journey