Message-based debugging facilities for Web or Grid Services are separated from an infrastructure of source level debugging and can work in a self-identifying and coexisting mode within a normal services container. In this paper, we discuss problems for services debugging and approaches we take. We present the operational model and context inspection of message-based debugging facilities. The facilities are able to trace service behaviors, dump debugging information, and manage states and behavioral breakpoints of debugged services. This model supports a mechanism of multi-user and multi-site service debugging without requiring programmers or developers to one by one duplicate full scenarios in multiple servers.