Flow step reference

Configure steps using available contract fields and compatible local destinations. This is a task reference for Studio operations; it is not a promise that every MongoDB aggregation stage is exposed.

Step	Purpose	Important configuration
Request	Start with the incoming document	Input contract
Validate Data	Check required values and types	Fields to validate and behavior
Set Fields	Assign fixed values, copies, or expressions	Destination and source/expression; never write input.*
Choose Fields	Select the fields retained in a working/result object	Source and retained fields; input remains immutable
Transform Each Item	Map list items	Source list, item expression/mapping, destination
Filter List	Keep matching items	Source list, item conditions, destination
Flatten List	Flatten nested lists	Source and destination
Sort List	Order list items	Sort fields/directions; in-place only for local lists
Trim List	Keep a range or count	Source, range/count, destination
Aggregate List	Calculate a list summary	List, operation, value field, destination
Check Exists	Test whether matching items exist	List, predicate, boolean destination
Lookup	Read reference-data values	Dataset/version, key mapping, result destination
If / Else	Route by conditions	Conditions and complete outgoing branches
Decision Table / Decision Tree	Call a decision asset	Dependency, input mappings, result destination
Call Flow	Call a reusable Flow	Dependency, input mappings, result destination
Response	Return the chosen response	Response mapping/shape compatible with Outputs

Do not infer support for collection-level stages such as $merge or $out from MongoDB documentation. Use the editor's actual palette and validate the completed Flow. Operator registration alone does not establish that a stage is available in Studio.