SUGGESTION: set_attributes

{
    "pools": [
        {
            "rolls": 1,
            "entries": [
                {
                    "type": "item",
                    "name": "minecraft:diamond_sword",
                    "weight": 1,
                    "functions": [
                        {
                            "functions": "set_attributes",
                            "attributes": [
                                {
                                    "attribute": "generic.attackDamage",
                                    "name": "More Damage",
                                    "amount": {
                                        "min": 3,
                                        "max": 6
                                    },
                                    "operation": 0,
                                    "slot": [
                                        "mainhand"
                                    ]
                                },
                                {
                                    "attribute": "generic.maxHealth",
                                    "name": "More Health",
                                    "amount": 2,
                                    "operation": 0,
                                    "slot": [
                                        "mainhand",
                                        "offhand"
                                    ]
                                }
                            ]
                        }
                    ]
                }
            ]
        }
    ]
}