Example DataPack JSON for Farming for Blockheads market (1.14+)

MarketRegistry.json

{
  "groupOverrides": {
    "Vanilla Seeds": {
      "enabled": false
    },
    "Vanilla Saplings": {
      "payment": {
        "item": "minecraft:diamond",
        "count": 3
      }
    }
  },
  "entryOverrides": {
    "minecraft:oak_sapling": {
      "enabled": false
    },
    "minecraft:bone_meal": {
      "amount": 12 
    }
  },
  "customCategories": {
    "wooden_stuff": {
      "name": "Wooden Stuff",
      "icon": {
        "item": "minecraft:stick"
      }
    }
  },
  "customEntries": [
    {
      "output": {
        "item": "minecraft:stick"
      },
      "payment": {
        "item": "minecraft:coal"
      },
      "category": "wooden_stuff"
    },
    {
      "output": {
        "item": "minecraft:oak_wood"
      },
      "payment": {
        "item": "minecraft:coal",
        "count": 2
      },
      "category": "wooden_stuff"
    },
    {
      "output": {
        "item": "minecraft:enchanted_book",
        "nbt": {
          "StoredEnchantments": [
            {
              "lvl": 3,
              "id": "minecraft:sharpness"
            }
          ]
        }
      }
    }
  ]
}