API/data type documentation for content, and other "Eleventy Supplied Data"

[francoposa]

It's possible I missed this but I cannot find in the docs site any real API doc or even direct reference to what exactly content is - it seems to be just sort of inferred that it's everything after the front matter in an input file (post rendering)? Are there any other wrinkles?

The page data type is well documented here: https://www.11ty.dev/docs/data-eleventy-supplied/#page-variable, as is the eleventy type below it: https://www.11ty.dev/docs/environment-vars/#eleventy-supplied.

In contrast content is only tangentially referred to under "collection item data structure": https://www.11ty.dev/docs/collections/#collection-item-data-structure. But considering content is listed at the top of the "Eleventy Supplied Data" page, it's confusing that it's not mentioned again at all on that page.
Even collections doesn't really have a doc of its full structure the same way that page does - as you read the guide you are introduced to the built-in collections.all then the tag-generated ones like collections.post. Are there other attributes? Do we just infer that that is all there is?

It would be super helpful if each of these few built-ins had a doc section as clear as the page data type, and we didn't have to jump around through several pages to sort of back into and assume what the structures are.

Thanks!