Both sys::Type.doc and sys::Slot.doc say:

If there is additional documentation meta-data available it is included an the start of the string as a series of "@name=value" lines.

How do you declare this meta-data in the Fandoc comment?

(I can't find it in the docs. Though I'm sure I've seen it mentioned and it's something to do with :'s)

Are there any common Fantom conventions for this meta-data, such as Since or See and if so, are they case-sensitive?

Is there a sample doc page on this site that shows how the meta-data is displayed?

Actually that format is obselete, it just returns the raw fandoc string.

The way api docs are packaged into a pod got completely reworked when I built the new compilerDoc module. The new format is a more complex plain text format (from compilerDoc::ApiDocParser)

** The syntax is defined as:
**   <file>      :=  <class> <slot>*
**   <class>     :=  "== " <name> <nl> <attrs>
**   <slot>      :=  (<fieldSig> | <methodSig>) <attrs>
**   <fieldSig>  :=  "-- " <name> <sp> <type> [":=" <expr>] <nl>
**   <methodSig> :=  "-- " <name> "(" <nl> [<param> <nl>]* ")" <sp> <return> <nl>
**   <param>     :=  <name> <type> [":=" <expr>]
**   <return>    :=  <type>
**
**   <attrs>     :=  <meta>* <facet>* <nl> <doc>.
**   <meta>      :=  <name> "=" <expr> <nl>
**   <facet>     :=  "@" <type> ["{" <nl> [<name> "=" <expr> <nl>]* "}"] <nl>
**   <doc>       :=  lines of text until "-- "
**
**   <name>      :=  Fantom identifier
**   <type>      :=  Fantom type signature (no spaces allowed)
**   <expr>      :=  text until end of line
**   <nl>        :=  "\n"
**   <sp>        :=  " "
**
** Standard attributes:
**   - base: list of space separated base class type signatures
**   - mixins: list of space separated mixin type signatures
**   - loc: <file> ":" <line> "/" <docLine>
**   - flags: type or slot space separated flag keywords
**   - set: field setter flags
**
** Note that the grammar is defined such that expr to display
** in docs for field and parameter defaults is always positioned at
** the end of the line (avoiding nasty escaping problems).

Okay, so looking at the code ApiDocParser it seems there is no custom @javadoc style meta-data. The only <attrs> parsed are few, very specific compiler ones like loc, mixins & facets.

In light of that, may I suggest the Fandoc for both Type and Slot are updated to just say:

Return the raw fandoc for this slot or null if not available.

The only thing worse than no documentation is wrong documentation!

Yes the attrs are compiler driven. I already updated the docs.

Ah, that's were I saw the other ref to meta-data: fandoc::index#header - is this meta also obsolete?

No that is still used (but only in stand alone documentation chapters)