pilou said:

I have never seen an event telling me that someone has been spying on me, but I have seen event telling me that my spying on someone else costed us both some of our scout.

So I suppose, in the latter case the other party knows that I have been spying on him. But are there conditions in which spying in totally stealthily and he doesn't see anything ? e.g.: If I use higher tier scouts than everything he has ?

so your enemy don’t see your scout march on the map but he will receive report after u’ve already scout him (if he has scouts at the city in this moment) so if u mean that then how it works (with any scout tiers)...but although smb can easy guess you espionage right if u lost shield for 1 sec near him :DD

Spy report on tiles does not come to enemy..i.e. If you spy resource tile of anyone then they wont even see that in report. But if someone spy on you then you will get report. If you succeeded to defend against spy attack then report of enemy will show just how many spy his/her spies killed. And if they defeat your spies then every detail of your town(military and rss) goes to enemy in report. BUT no one can see spying march except the one who is spying.

In fact, that should mean that you need spies to detect spies - and you probably won't get a report if you don't have any spies in town either... which will be logical since you cannot have a report of your spies dying if you don't have any.

That the reason why I wonderer if higher tier spies would stay unseen from lower tiers.

Crime said:

I will have to see that and yes i will remove spies from my town and then see how does spy report works and will update here. And yes CIM we get no report of spying on tiles unless u r caught without shield for just a second. And yes spies level matter as much as other troops level so dont get confused with it. They do same stuff like troops...tho they work only against other spies...and yes one cannot even onslaught with spies. There needs to be a single attacker and defender for spies.

I mean spy level doesn't matter on whether you get a report about spying on towns ... that was his question ... in OP he asked if he used higher level spies on them than they have (in town) then will they NOT get a report and I said spy level doesn't matter (meaning for that). 

pilou said:

In fact, that should mean that you need spies to detect spies - and you probably won't get a report if you don't have any spies in town either... which will be logical since you cannot have a report of your spies dying if you don't have any.

That the reason why I wonderer if higher tier spies would stay unseen from lower tiers.

if u don’t have any spies - u can’t detect enemy espionage bcz spies fighting (read “see”) only with spies.  

so if u can’t detect enemy espionage u don’t get report about it (logic),

so while u can’t send spies on the tile if there is no enemy warriors (noone to scout) and spies’s capacity = 0 (so they can’t yield smth) even adding to your main troops u cant detect enemy espionage on YOUR tiles  

enemy can scout you on tile always invisible for u (as i say bcz u can’t sent your spies to sit there and detect enemy spies), btw you too can do it even u’ll send 1 spy there he will get full report 

and so in the town the same mechanic =  if u have no spies in your town (they’re dead or u send they somewhere) u can’t detect enemy espionage and don’t get report about it  

but even u have just 1 scout tier 1 inside your town, he will bravely detect the espionage fact and send you a report  :)