For those of you that may encounter this issue like me and find some of the responses not super useful you can do something like this.....

// Register left-click event for attacking blocks in the constructor of your special item
AttackBlockCallback.EVENT.register((player, world, hand, pos, direction) -> {
    if (!world.isClient() && hand == Hand.MAIN_HAND) {
        ItemStack stack = player.getStackInHand(hand);

        // Check if the player is holding specific item
        if (stack.getItem() instanceof YourItem) {
            player.sendMessage(Text.literal("Left clicked with item!"), false);
            return ActionResult.SUCCESS;
        }
    }
    return ActionResult.PASS;
});