I can't seem to get only very high skill games.

https://api.steampowered.com/IDOTA2Match_205790/GetMatchHistory/v001/?key=<key>&skill=3

{
"result": {
"status": 1,
"num_results": 0,
"total_results": 0,
"results_remaining": 0,
"matches": [

]

}
}