Transform Step

TransformStepDescription reshapes data without an LLM call — cheap, fast, and deterministic. Good for formatting, extracting, or aggregating prior output.

TransformStepConfig

Field	Type	Default	Purpose
transform_type	"extract" | "format" | "aggregate" | "filter" | "map"	— (required)	The kind of transformation.
input_key	str	"$history[-1]"	Where the input comes from.
output_format	str | None	None	Output template (for format).
expression	str | None	None	Expression for extract / filter.
map_template	str | None	None	Per-item template for map.

Example

from mmar_carl import TransformStepDescription, TransformStepConfig

TransformStepDescription(
    number=3,
    title="Format summary",
    dependencies=[2],
    config=TransformStepConfig(
        transform_type="format",
        input_key="$history[-1]",
        output_format="Summary: {value}",
    ),
)

See also

• Building chains — the add_transform_step() shortcut.
• Dynamic references — what input_key accepts.