broken item tags

I was testing some commands and noticed that the "CanDestroy" tag seems to be broken. Any time I attempt to use it, I get the error "line 1, column 2, missing '}' or object member name". I've attempted using "minecraft:item_name" and "item_name" and the same error pops up. regardless of how I use the command
For reference, I wanted to make an axe that coulf only break wall signs
"/give iron_axe 1 0

{CanDestroy ["minecraft:wall_sign"], Unbreakable: true}

"
The syntax helper dimmed out and upon running the command, the above error popped up. I then tried changing "minecraft:wall_sign" to "wall_sign" and to no avail. Even went as far as using "sign" instead of "wall_sign" and still no results...