OptionaldefinitionPending effects dispatched to a registered handler in this drain — 0 for an empty poll (the pass itself is the signal).
The dispatched effects' author-chosen names, in drain order — one of the payload policy's two deliberate customer-string exceptions (module doc).
The instance document _id — the per-instance join key (engine-minted
<tag>.wf-instance.<random>; caller-supplied ids ride verbatim). One of
the payload policy's two deliberate customer-string exceptions — see the
module doc.
Absent only when the definition predates content fingerprinting.