class

Classes consist of a name, a list of properties, and their types. In the context of LLMs, classes describe the type of the variables you can inject into prompts and extract out from the response.

Note properties have no :

1 class Foo {
2   property1 string
3   property2 int?
4   property3 Bar[]
5   property4 MyEnum
6 }

Field Attributes

When prompt engineering, you can also alias values and add descriptions.

@alias

string

Aliasing renames the field for the llm to potentially “understand” your value better, while keeping the original name in your code, so you don’t need to change your downstream code everytime.

This will also be used for parsing the output of the LLM back into the original object.

@description

string

This adds some additional context to the field in the prompt.

BAML

1 class MyClass {
2   property1 string @alias("name") @description("The name of the object")
3   age int? @description("The age of the object")
4 }

Class Attributes

@@dynamic

If set, will allow you to add fields to the class dynamically at runtime (in your python/ts/etc code). See dynamic classes for more information.

BAML

1 class MyClass {
2   property1 string
3   property2 int?
4 
5   @@dynamic // allows me to later propert3 float[] at runtime
6 }

Syntax

Classes may have any number of properties. Property names must follow these rules:

Must start with a letter
Must contain only letters, numbers, and underscores
Must be unique within the class
classes can be recursively defined!

The type of a property can be any supported type

Default values

Not yet supported. For optional properties, the default value is None in python.

Dynamic classes

See Dynamic Types.

Inheritance

Never supported. Like rust, we take the stance that composition is better than inheritance.

1	class Foo {
2	property1 string
3	property2 int?
4	property3 Bar[]
5	property4 MyEnum
6	}

1	class MyClass {
2	property1 string @alias("name") @description("The name of the object")
3	age int? @description("The age of the object")
4	}