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Resource Orchestration Service:Fn::Add

Last Updated:Jun 17, 2026

Fn::Add calculates the sum of numbers, combines lists, or merges dictionaries.

Declaration

JSON

{
  "Fn::Add": [
    {k1: v1},
    {k2: v2}
  ]
}

YAML
- Syntax for the full function name:
```
Fn::Add:
  - k1: v1
  - k2: v2
```
- Syntax for the short form:
```
!Add [{k1: v1}, {k2: v2}, ...]
```

Parameters

Parameters must be provided as a list.
All parameters in a list must be of the same type: Number, List, or Dictionary. A list must contain at least two parameters.

Return value

Number: returns the sum of all values.
List: returns a single combined list.
Dictionary: returns a merged dictionary. If dictionaries share the same key, the latter value overwrites the former.

Examples

Dictionary parameters
```
!Add
  - key1: value1
  - key2: value2
```
Returns {"key1": "value1", "key2": "value2"}.
List parameters
```
!Add
	- - list_1_value_1
  	- list_1_value_2
  - - list_2_value_1
  	- list_2_value_2
```
Returns ["list_1_value_1","list_1_value_2","list_2_value_1","list_2_value_2"].
Number parameters
```
!Add
 - 1
 - 2
 - 3
```
Returns 6.