One model as a single panel: columns, keys, associations.
Every model on one sheet, with the relationships drawn between them.
Chen notation — entities, diamond relationships, oval attributes.
Crow's-foot relational schema.
UML class diagram: attributes, methods, visibility.
What one migration changes: tables and columns added, altered, dropped.
Reference-style schema documentation, table by table.
Indexes per table, and the columns they cover.
Which models depend on which.
Messages exchanged between participants, in order.
States and the transitions between them.
Nodes and edges — a general flowchart.
A hierarchy.
Modules grouped into packages.
A schedule, as bars on a timeline.
Every diagram this package can render.
The values are stable lowercase slugs, safe to accept from a CLI flag, a query string or a JSON config, and safe to persist.