Can you tell that which is the best tool to monitor WCF services, WMI or WS-Discovery implementation.
The requirements look easy, but in fact it's quite difficult. Service may be available but operations may fails and vice-versa. There are also many potential problems : network failure, pool/service host stopped, wcf activation fails, operation errors... A service can be available but all operations fails because of a corrupt database. WMI/Perf counters seems to be a good approach as you can have many details for different scopes (service/operation/endpoint). But In addition if your hosting your service under IIS, application pool idle default timeout is 20 minutes: counters/WMI will be unavailable.
In conclusion, i would said that the best monitoring strategy is an agregation of all tools/components available to server side and to client side.