rules.json

[
    {
        // match will find entities matching all these key-values
        "match":
        {
            "classname": "monster_barney",
            "models": "models/barney2.mdl"
        },
        // not_match opposite as match, requires the entity to NOT have these key-values
        "not_match":
        {
            "weapons": "1"
        },
        // have requires the matched entity to have this keys
        "have":
        [
            "body",
            "skin"
        ],
        // not opposite as have, requires the entity to not have these keys
        "not_have":
        [
            "spawnflags"
        ],
        // replace will replace all these keyvalues
        "replace":
        {
            "models": "models/mymod/barney.mdl"
        },
        // rename will rename the key keeping the value
        "rename":
        {
            "body": "bodygroup"
        },
        // add will add this key-vaue
        "add":
        {
            "weapons": "1"
        },
        // remove will remove these key-value from this entity
        "remove":
        [
            "skin"
        ],
        // new_entity wil add all these entities for each matched entity
        "new_entity":
        [
            {
                "classname": "env_sprite_follow",
                "target": "$targetname"
            }
        ]
        // Adding a dollar sign ($) means we'll use the original entity's value of the given key
        // Example "$origin" means we'll use the origin of the matched entity.
    },
    {
        // This rules will be only applied to these maps.
        "maps": [
            "c1a0",
            "c1a1"
        ]
    }
]