How do I spawn a zombie with an item from a mod?

I'm trying to get every achievement related to the Inventory Pets mod but I need to kill a player holding a specific item from that mod, Is there any way I could spawn a zombie holding this item? I've already tried

/summon zombie ~ ~1 ~ {HandItems:[{id:inventorypets:cobblestone_pet} 

but that returns

Data tag parsing failed: Expected '}' but got ':' at: {HandItems:[{id:inventorypets:<--[HERE]

Is there any way I could make this work?

Solution 1:

You need to put quotes around your string:

/summon zombie ~ ~1 ~ {HandItems:[{id:"inventorypets:cobblestone_pet"}]}

Since your value had a colon :, which is a non-alphanumeric character and not an underscore (_), it is not assumed to be a string. To make the entire thing a string, quotes must be added. Otherwise, Minecraft stops reading the string at the second colon, being invalid because it expects a comma , to start the next key-value pair.

It thinks the colon is something entirely different, so you have to tell it that that is part of your string by adding the quote marks.