# catalog.json (/docs/agents/catalog)

> The machine index of Section types, Themes, Templates and docs addresses, in the shape startupbuilder.dev's sync reads.

`https://next.mdxui.dev/catalog.json` holds, for `@mdxui/site@7.0.0-alpha.0`:

| Key | Holds |
| --- | --- |
| `sectionTypes` | Each Section type: its group, job, glyph, fields and bounds, variants with their frame addresses, its schema and its docs page |
| `themes` | Each Theme: typefaces, policies, whether it emits dark, and the landing rendered in it |
| `templates` | Each Template and the worked-Site pages that use it |
| `docs` | The docs addresses an agent starts from |

startupbuilder.dev owns the definitions of the Components these types draw. Its proposed `mdxui-sync` takes three fields per Section type from this file, and only from types whose page is accepted: an example record, stills and the docs address. It takes no definition, prop or bound; those stay on each side as they are.