File Metadata Definition

Name	Type	Required	Meaning
id	int	For Updates	A unique identifying integer.
fileId	int	Yes	The ID of the file the metadata belongs to. Required on create and must reference a file you have access to; fixed on update (any other value is ignored).
key	string	Yes	The name of the metadata. Must be 300 or fewer characters in length.
value	string	Yes	The metadata. Must be 300 or fewer characters in length.