_        _______           _______  _             ___   
( \      (  ____ \|\     /|(  ____ \( \           /   )  
| (      | (    \/| )   ( || (    \/| (          / /) |  
| |      | (__    | |   | || (__    | |         / (_) (_ 
| |      |  __)   ( (   ) )|  __)   | |        (____   _)
| |      | (       \ \_/ / | (      | |             ) (  
| (____/\| (____/\  \   /  | (____/\| (____/\       | |  
(_______/(_______/   \_/   (_______/(_______/       (_)  

Object in S3, including its metadata, is immutable. When you edit object's metadata, you are actually overwriting the object with a copy of itself, with its metadata modified. In contrast, tags are subresources. They are managed separately and can be modified without modifying the object itself.

Each tag is a key-value pair. You can associate up to 10 case-sensitive tags with an object.

Hint 2
To get objets'tags use get-object-tagging command.

{
    "TagSet": [
        {
            "Key": "secret_code",
            "Value": "xxx"
        }
    ]
}