Choosing a strategy via JSON config

I am implementing a learning agent in Java/Kotlin. Part of this agent's functionality involves it searching through a large list of possible options. There are multiple good ways to search the possibility space, and I frequently change my mind about which one is the best. Therefore, I decided to implement it as a strategy pattern.

class Agent(val searchStrategy : SearchStrategy){
    fun search(input : InputGraph) : Result{
        return searchStrategy.search()
    }
}

interface SearchStrategy{
    fun search(input : InputGraph) : Result
}

class FastSearch : SearchStrategy{
    //implementation here
}

class AccurateSearch : SearchStrategy{
   // implementation here
}

class ExperimentalSerach : SearchStrategy{
  // implentation here
}

Recently, I've decided to run a large suite of experiments which test the effectiveness of various system parameters. This is done through a python script, which kicks of each experiment by running the compiled jar with a different config.json file as an argument. Something like:

{
    "numSamples" : 5000,
    "environmentDifficulty" : 3,
    "hazardProbability" : 0.4,
    //etc..
}

I now want to give the experimenter the ability to configure the strategy used by the agent as well. What is the best way to do this? My immediate thought is that I could just add an additional string field to the config.json:

{
    "numSamples" : 5000,
    "environmentDifficulty" : 3,
    "hazardProbability" : 0.4,
    "agentStrategy": "FastSearch"
}

Then construct it in the main system with an when or if branch:

val searchStrategy = when(config.agentStrategy){
    "FastSearch" -> FastSearch()
    "AccurateSearch" -> AccurateSearch()
    "ExperimentalSearch" -> ExperimentalSearch()
val agent = agent(searchStrategy)

But this seems like it will start to get awkward / difficult to maintain if I begin to add more strategies. Is there a better way?