Brainstorming a simple API description format, generic but with Haxe externs in mind

Example.js

// The format is JSON, but using js for comments.
{
	// Type (Starts with Uppercase to differentiate from the primitive types)
	"IncomingForm": {
		"" : "Empty key leaves room for a description.",
		// A function ends with (). Array value signifies overloading
		"parse()": [{ 
			"" : "Parse a form",
			// Parameter: Type
			"req": "js.npm.express.Request",
			// Parameter: Function
			"cb": ["mixed", "mixed", "array<File>", "void"],
		}, { 
			"req": "js.npm.express.Request",
			// Parameter: function with Haxe-syntax. Easier to use?
			"cb": "mixed -> mixed -> File -> void",
		}],

		// Object = only one signature, no overloads
		"test()": {
			"param": "mixed",
			// -> for return value (if not specified void is assumed)
			"->": "IncomingForm"
		}
	},

	"File": {
		"size": "integer",
		"path": "string",
		"name": "string",
		"type": "string",
		"lastModifiedDate": "date",
		"hash": "string",

		// String = no parameters, return value only.
		"toJSON()" : "mixed"
	}
}

Primitive_types.txt

integer		signed 32 bits
long		signed 64 bits
float		
double			
string			
byte			
boolean				
date		as defined by full-date - RFC3339
dateTime	as defined by date-time - RFC3339
mixed		any type
void		no return value
array