What are the valid data types for API Blueprint?

I'm just wondering what are the valid datatypes when working with API Drawings?

The documentation seems confusing to me. More specifically, it says:

type is an optional parameter type as expected by the API (for example, "number", "string", "boolean"). "String" by default.

Does it mean:

• Are only "number", "string" and "boolean" valid?
• JSON primitive types expected ?
• Other?