Thanks for your help. Unfortunately I can't generate Add-ins, because installations are forbidden 😞
So I tried this simple solution:
import arcpy
import os
input = arcpy.GetParameterAsText(0)
clipfeature = arcpy.GetParameterAsText(1)
output = arcpy.GetParameterAsText(2)
arcpy.env.workspace = output
inputSp = input.split(";")
for i in inputSp:
arcpy.AddMessage(i)
arcpy.Clip_analysis(i, clipfeature, i)