@btcmaker-io You can't view things inside unless you open them. In order to open them you have to send c08 (essentially right click) which could flag you for reach.
//requires core
onJump: function(e) {
if (BlockUtils.getBlock(new BlockPos(mc.thePlayer).down(1)) != Blocks.slime_block)
e.cancelEvent();
}
What is core?