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Step reference / Transform

Step reference · Data

Transform

Reshape what one step produced into what the next one needs. There is no separate transform step: a step’s Input mapping does it, with the same expressions conditions use.

DataTransform
Written as
Input mapping
Reads
{ Field: Read.Lines }
Nodes
Filter, Map, Length, Add…
Transform has no step kind of its own. It is the Input mapping of the step that needs the reshaped value.

Inputs

<field>: { Field: path }expression
Reads a value: Trigger for the request, or a step’s name for its output, then its fields.
<field>: <literal>literal
A number, string, true or false, list or object, taken as written.
<field>: { <node>: … }expression
Any expression node below, evaluated when the step runs.

Outputs

<mapped input>object
The object the mapping builds, which the step is called with. A path that resolves to nothing leaves its field out.

Expression nodes

NodeArgumentsGives
Map
Over, As, Body
Each item turned into a new value
Filter
Over, As, When
The items the condition holds for
Aggregate
Over, As, Into, Body
One value folded from every item
Length
Of
How many items or characters
Sort
Over, By, Descending
The items in order
Unique
Over
The items without repeats
Range
From, To
A list of numbers
Add, Subtract, Multiply, Divide, Modulo
Left, Right
A number
Concat
Left, Right
Two strings joined
If
When, Then, Else
One of two values
Let
Name, Value, In
A value named for the expression inside it
FunctionCall
Function, Args
What a declared function returns

Example

- ExecuteTool: Notify
  Operations: [PostMessage]
  Input:
    channel: finance
    overdue:
      Filter:
        Over: { Field: Read.Invoices }
        As: Invoice
        When: { GreaterThan: { Field: Invoice.DaysLate, Value: 30 } }
    count:
      Length:
        Of: { Field: Read.Invoices }

Reusing an expression

Declare an expression once under Functions and call it anywhere with FunctionCall. Its parameters are its only names: the body reads them, not the run’s values.

Functions:
  - Name: OverLimit
    Parameters: [Amount, Limit]
    Body:
      GreaterThan:
        Field: Amount
        Value: { Field: Limit }

Steps:
  - Branch: Check
    Cases:
      - When:
          FunctionCall:
            Function: OverLimit
            Args:
              Amount: { Field: Read.Amount }
              Limit: 500
        Then:
          - Wait: Approve
            Operation: Clarification
            Question: This refund is over the limit. Approve it?
Bounded and repeatableAn expression gives the same value every time it reads the same values, and it cannot loop forever: every evaluation stops at the deployment’s expression ceiling, 1,000 nodes by default. A model step is the place for work that needs judgment.
Updated Oct 22, 2026
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