I'm having trouble making a tool that can break certain things in Minecraft Bedrock [duplicate]

The example given in the wiki should potentially help you identify the issues you are having with your command

/give @p iron_shovel 1 0 {"minecraft:can_destroy":{"blocks":["grass"]}}

And the syntax for adding an enchantment, I believe also needs to be specified as well:

/give @r diamond_sword{Enchantments:[{id:"minecraft:sharpness",lvl:10}]} 1

As you can see my comparison, there are potentially a few mismatches in the syntax. So your command should look like this:

/give @p diamond_shovel{Enchantments:[{id:"minecraft:unbreakable",lvl:1}]} 1 0 {"minecraft:can_destroy":{"blocks":["grass"]}}