On Block - apace100/origins-fabric GitHub Wiki

Entity Condition. Checks whether the player is standing on the ground, and optionally has a block that matches a specified block condition under them.

Type ID: origins:on_block

Fields:

block_condition, Block Condition, optional: If set, a block that satisfies this block condition needs to be right below the player's feet.

Example:

"condition": {
  "type": "origins:on_block",
  "block_condition": {
    "type": "origins:block",
    "block": "minecraft:grass"
  }
}

This condition applied to a power will make sure it's only active while the player is on grass.