Scoped Arguments

Scoped arguments are $-prefixed identifiers that name a value injected by an enclosing construct. They are read through the $arg expression:

{ "$arg": "$item" }

{ "$arg": "$0" }

Required

• $arg (string): The scoped argument name (e.g. "$item", "$index", "$content", "$0", "$1").

Returns: The value of the referenced argument.

Available Arguments

Each construct injects its own arguments, valid only within its scope:

A document MUST NOT reference a scoped argument outside the scope of the construct that injects it. Schema validation cannot check dynamic scope, so an out-of-scope reference surfaces at resolution time: it is an error, and engines MUST report it.

Scopes nest lexically: a construct's injected arguments stay visible throughout its scope, including inside nested constructs, and an inner construct injecting an argument of the same name shadows the outer one within its own scope. An action inside a map template reads both $item and, when its callback fires, $0.

Accessing Nested Values

Append a JSON Pointer path to the identifier: the identifier runs to the first /, and the rest is an RFC 6901 pointer into the value:

{ "$arg": "$0/email" }

{ "$arg": "$0/1" }

{ "$arg": "$item/name" }

Here $0/email reads the email property of the first positional argument, $0/1 reads the second element of an array argument, and $item/name reads the name property of the current map item. A pointer that names no value resolves to undefined, as with data references.