Types Overview

BAML provides a rich type system for defining inputs and outputs of AI functions.

Primitive Types

Type	Description
bool	Boolean value (true or false)
int	Integer number
float	Floating point number
string	Text data
null	Null/empty value

Composite Types

Type	Syntax	Description
class	class Name { ... }	User-defined structured data
enum	enum Name { ... }	Set of named constants
array	Type[]	Collection of elements
map	map<KeyType, ValueType>	Key-value pairs
optional	Type?	Value that may be absent
union	Type1 | Type2	One of several types
literal	"value" or 1 or true	Specific constrained value
type alias	type Name = Type	Alternative name for a type

Multimodal Types

Type	Description
image	Image data (URL or base64)
audio	Audio data (URL or base64)
pdf	PDF document (base64 only)
video	Video data (URL or base64)

Type Examples

// Primitives
function GetCount() -> int { ... }
function GetName() -> string { ... }

// Arrays
function GetNames() -> string[] { ... }

// Optional
function GetAge() -> int? { ... }

// Union
function Classify() -> "bug" | "feature" | "question" { ... }

// Complex
class Person {
    name string
    age int?
    tags string[]
}

function ParsePerson(text: string) -> Person { ... }

Unsupported Types

Type	Alternative
any/json	Use string and parse manually, or use dynamic types
datetime	Use string
duration	Use string with ISO8601 format
set	Use array (Type[])
tuple	Use class

See Also

• Primitives
• Arrays
• Maps
• Classes and Enums
• Multimodal Types