Use when designing or reviewing a component's public API. Naming, props, compound component structure, CSS custom properties, and data-attributes.
Use when writing something public-facing about this project's engineering. A release announcement, a how-we-built-X deep-dive, a retrospective. Not tied to a release event, and not the mechanical changelog (that's changeset-writing's job).
Use when a feature involves multiple states or transitions. Recognizes the shape, names states and events, designs guards, actions, and hierarchy, and visualizes or simulates the result.
Use when writing a changeset for a change to a published package. Picking the semver bump, writing the summary, flagging breaking changes, and making sure the entry still reads well once aggregated into CHANGELOG.md.