With the code of Market API , Apk downloader, Playframework and some other code (reverse the .proto from apk downloader), I made a google play crawler. link

Here’s the .proto used the same way as in apk downloader

package com.google;

message MarketRequest {
		required AuthBody auth = 1;
		required group Pack = 2 {
			optional PackageName packageName = 10;  // android id converted to hexadecimal
		}
}

message PackageName{
	required string name = 1;;
}

message AuthBody{
        required string authSubToken = 1; // authsub token for service 'android'
        required bool isSecure = 2; // is this a secure request or not
        required int32 version = 3;  // always 1002
        required string deviceId = 4;  // android id converted to hexadecimal
        optional string deviceAndSdkVersion = 5; // ro.product.device ':' ro.build.version.sdk 
        optional string locale = 6; // ro.product.locale.language
        optional string country = 7; // ro.product.locale.region
        optional string operatorAlpha = 8; // gsm.operator.alpha
        optional string simOperatorAlpha = 9; // gsm.sim.operator.alpha
        optional string operatorNumeric = 10; // gsm.operator.numeric
        optional string simOperatorNumeric = 11; // sim.gsm.operator.numeric
}

package com.google;

message MarketResponse {
	required group RespBody = 1{
		required bytes header1 = 2;
		required AppInfo info = 9;
	}
}

message AppInfo {
	required group AppInfoBody = 1 {
		required string appId = 2;
		required string appName = 3;
		required string type = 4;
		required string packageName = 5;
		required string downloadUrl = 6;
		required string ParamGroup = 7;
		required int32 someId1 = 8;
		required int32 someType1 = 10;
		required int32 someType2 = 11;
		required int32 someId3 = 12;
		required string market = 13;
		required string marketDA = 14;
	}
}