Schemas that adapt at runtime

Sometimes you don't know your schema until runtime—user-configured forms, database-driven fields, or plugin systems.@@dynamic and TypeBuilder let you add properties on the fly.

Mark a class with @@dynamic in BAML, then use TypeBuilder in your code to add fields before calling the function.

main.baml
// BAML Definition - mark class as @@dynamic
class FormField @@dynamic {
  label string
  value string
}

function ExtractForm(image: image) -> FormField[] {
  client "openai/gpt-4o-mini"
  prompt #"
    Extract all form fields from this image:
    {{ image }}

    {{ ctx.output_format }}
  "#
}
Click Run to see the rendered prompt
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