array (list) | Boundary Documentation

Allow you to store and manipulate collections of data. They can be declared in a concise and readable manner, supporting both single-line and multi-line formats.

Syntax

To declare an array in a BAML file, you can use the following syntax:

{
  key1 [value1, value2, value3],
  key2 [
    value1,
    value2,
    value3
  ],
  key3 [
    {
      subkey1 "valueA",
      subkey2 "valueB"
    },
    {
      subkey1 "valueC",
      subkey2 "valueD"
    }
  ]
}

Key Points:

Commas: Optional for multi-line arrays, but recommended for clarity.
Nested Arrays: Supported, allowing complex data structures.
Key-Value Pairs: Arrays can contain objects with key-value pairs.

Usage Examples

Example 1: Simple Array

function DescriptionGame(items: string[]) -> string {
    client "openai/gpt-5-mini"
    prompt #"
        What 3 words best describe all of these: {{ items }}.
    "#
}
test FruitList {
    functions [DescriptionGame]
    args { items ["apple", "banana", "cherry"] }
}

Example 2: Multi-line Array

test CityDescription {
    functions [DescriptionGame]
    args { items [
            "New York",
            "Los Angeles",
            "Chicago"
        ]
    }
}